
Class Q_X1 30 

Book 



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FOWNES' 



MANUAL OF CHEMISTRY, 



V v 



ELEMENTARY 



CHEMISTRY, 



THEORETICAL AND PRACTICAL 



BY 



GEORGE FOWNES, F.R.S., 

LATE PROFESSOR OF PRACTICAL CHEMISTRY IN UNIVERSITY COLLEGE, LONDON. 



EDITED, WITH ADDITIONS, 



ROBERT BRIDGES, M. D., 

PROFESSOR OF CHEMISTRY IN THE PHILADELPHIA COLLEGE OF PHARMACY, ETC. KTO. 

A NEW AMERICAN, 

FROM TttE LAST AND REVISED LONDON EDITION. 



WITH NUMEROUS ..ILLUSTRATIONS ON VfOOD. 




PHILADELPHIA: 
BLANC HARD AND LEA, 

1858. 



$ 



& 



A\& 



V 



Entered, according to Act of Congress, in the year 1853, by 
B LAN CHARD AND LEA, 

in the Clerk's Office of the District Court of the United States for ths 
Eastern District of Pennsylvania. 



BY TRANSFER 
u» ft t90fi 



Prime J bv T. X & P. G Collins. 



ADVERTISEMENT 



NEW AMERICAN EDITION 



The lamented death of the Author has caused the revision of this 
edition to fall into the hands of others, who have fully sustained its 
reputation by the additions which they have made, more especially 
in the portion devoted to Organic Chemistry, as set forth in their 
preface. This labour has been so thoroughly performed, that 
the American Editor has found but little to add, his notes con- 
sisting chiefly of such matters as the rapid advance of the science 
has rendered necessary, or of investigations which had apparently 
been overlooked by the Author's friends. These additions will be 
found distinguished by his 'initials.' 

The volume is therefore again presented as an exponent of the 
most advanced state of Chemical Science, and as not unworthy a con- 
tinuation of the maiked favour which it has received as an elementary 
text-book. 

Philadelphia, 

October, 1853. 

1* (v) 



PREFACE. 



The design of the present volume is to offer to the student com- 
mencing the subject of Chemistry, in a compact and inexpensive 
forin, an outline of the general principles of that science, and a history 
of the more important among the very numerous bodies which Che 
mical Investigations have made known to us. The work has no pre- 
tensions to be considered a complete treatise on the subject, but is 
intended to serve as an introduction to the larger and more compre- 
hensive systematic works in our own language and in those of the 
Continent, and especially to prepare the student for the perusal of 
original memoirs, which, in conjunction with practical instruction in 
the laboratory, can alone afford a real acquaintance with the spirit of 
research and the resources of Chemical Science. 

It has been my aim throughout to render the book as practical as 
possible, by detailing, at as great length as the general plan permitted, 
many of the working processes of the scientific laboratory, and by 
exhibiting, by the aid of numerous wood-engravings, the most useful 
forms of apparatus, with their adjustments and methods of use. 

As one principal object was the production of a convenient and 
useful class-book for pupils attending my own lectures, I have been 
induced to adopt in the book the plan of arrangement followed in 
the lectures themselves, and to describe the non-metallic elements 
and some of their most important compounds before discussing the 
subject of the general philosophy of Chemical Science, and even 

(vii) 



Vlll PREFACE. 

before describing the principle of the equivalent quantities, or ex- 
plaining the use of the written symbolical language now universal 
among chemists. For the benefit of those to whom these matters 
are already familiar, and to render the history of the compound bodies 
described in the earlier part of the work more complete, I have added 
in foot-notes the view adopted of their Chemical constitution, ex- 
pressed in symbols. 

I have devoted as much space as could be afforded to the very im- 
portant subject of Organic Chemistry; and it will, I believe, be found 
that there are but few substances of any general interest which have 
been altogether omitted, although the very great number of bodies to 
be described in a limited number of pages rendered it necessary to 
use as much brevity as possible. 

GEO. FOWNES. 

University College, London, 
October 5, 1847. 



ADVERTISEMENT 



THIRD LONDON EDITION, 



The correction of this Edition for the press was the daily occupa- 
tion of Professor Fownes, until a few hours previous to his death in 
January, 1849. 

His wish and his endeavour, as seen in his manuscript, were to 
render it as perfect and as minutely accurate as possible. 

When he had finished the most important part of the Organic 
Chemistry, where the most additions were required, he told me he 
should "do no more," — he had "finished his work." 

At his request I have corrected the press throughout, and made a 
few alterations that appeared desirable in the only part which he had 
left unaltered, the Animal Chemistry. 

The index and the press have also been corrected throughout by 
his friend Mr. Robert Murray. 



H Bence Jones, M.D. 



30, Grosvenor Street, 
Jan., 1850. 



(ix) 



ADVERTISEMENT 



FOURTH LONDON EDITION 



It lias been the endeavour of the Editors to include in the present 
edition of the Manual the progress of Chemistry since the Author's 
death. 

The foundation which he laid, and the form which he gave to the 
work, remain untouched. But time has rendered it necessary that 
each portion should be revised ; and a few repairs, and some consider- 
able additions, especially in Organic Chemistry, have been made. 
Thus, several of the chapters on the Alcohols, the Organic Bases, 
Colouring Matters, &c, have been almost re-written. 

Still, such changes only have been made as the Editors believed 
the Author himself would have desired, if his life had been spared 
to Science. 

II. Bence Jones. 
A. W. Hofmann. 

London, September, 1852. 



(xi) 



TABLE OF CONTENTS, 



PAGE 

Introduction , « 25 



PART I. 

PHYSICS. 

Of density and specific gravity. 

Methods of determining the specific gravities of fluids and solids 27 

Construction and application of the hydrometer 32 

Of the physical constitution of the atmosphere, and of gases in 

GENERAL. 

Elasticity of gases. — Construction and use of the air-pump 34 

Weight and pressure of the air. — Barometer 37 

Law of Mariotte; relations of density and elastic force; correction of 

volumes of gases for pressure 38 

Heat. 

Expansion. — Thermometers 41 

Different rates of expansion among metals; compensation-pendulum 44 

Danieli's pyrometer , 45 

Expansion of liquids and gases. — Ventilation. — Movements of the atmo- 
sphere 46 

Conduction of heat 52 

Change of state. — Latent heat 52 

Ebullition; steam 54 

Distillation 58 

Evaporation at low temperatures 59 

Vapour of the atmosphere; hygrometry 61 

Liquefaction of permanent gases 62 

Production of cold by evaporation , 64 

Capacity for heat. — Specific heat &d 

Sources of heat 68 

2 (xiii) 



XIV CONTENTS. 

Light. 

page 

Reflection, refraction, and polarization of light 71 

Chemical rays 77 

Radiation, reflection, absorption, and transmission of heat 79 

Magnetism. 

Magnetic polarity; natural and artificial magnets 86 

Terrestrial magnetism 88 

Electricity. 

Electrical excitation; machines 92 

Principle of induction ; accumulation of electricity 93 

Voltaic electricity 97 

Thermo-electricity. — Animal electricity 99 

Electro-magnetism ; magneto-electricity 100 

Electricity of steam 103 



PART II. 

CHEMISTRY OF THE ELEMENTARY BODIES. 

Non-metallic elements. 

Oxygen 105 

Hydrogen; water; binoxide of hydrogen 110 

Nitrogen; atmospheric air ; compounds of nitrogen and oxygen 120 

Carbon; carbonic oxide ; carbonic acid , 127 

Sulphur; compounds of sulphur and oxygen 131 

Selenium 136 

Phosphorus; compounds of phosphorus and oxygen 137 

Chlorine; hydrochloric acid. — Compounds of chlorine and oxygen 139 

Iodine 143 

Bromine ... 148 

Fluorine 149 

Silicium 150 

Boron , 151 

Compounds formed by the union of the non-metallic elements among 
themselves. 

Compounds of carbon and hydrogen. — Light carbonetted hydrogen; olefiant 

gas; coal and oil-gnses. — Combustion, and the structure of flame 153 

Nitrogen and hydrogen; ammonia 162 



CONTENTS. XV 

PAG 3 

Sulphur, selenium, and phosphorus, with hydrogen 163 

Nitrogen, "with chlorine and iodine; chloride of nitrogen 167 

Other compounds of non-metallic elements 168 

Chlorine, with sulphur and phosphorus 168 

Dn the general principles of chesiical philosophy. 

Nomenclature 170 

Laws of combination by weight 172 

By volume . 177 

Chemical symbols ISO 

The atomic theory 182 

Chemical affinity 1S3 

Electro-chemical decomposition; chemistry of the voltaic pile 187 

Metals. 

General properties of the metals 197 

Crystallography 202 

Isomorphism 209 

Polybasic acids 212 

Binary theory of the constitution of salts 213 

Potassium 217 

Sodium 224 

Ammonium 232 

Lithium 235 

Barium 237 

Strontium 239 

Calcium 239 

Magnesium 245 

Aluminium 248 

Beryllium (glucinum) 250 

Yttrium, cerium, lanthanium, and didymium 251 

Zirconium. — Thorium 252 

Manufacture of glass, porcelain, and earthenware 252 

Manganese 256 

Iron 259 

Aridium 266 

Chromium 267 

Nickel 269 

Cobalt 271 

Zinc 272 

Cadmium 274 

Bismuth 274 

Uranium 276 

Copper 277 

Lead 279 

Tin 282 



XVI CONTENTS. 

PAOE 

Tungsten 284 

Molybdenum 284 

Vanadium 285 

Tantalum (columbium) 286 

Niobium and pelopium 286 

Titanium 287 

Antimony 287 

Tellurium , 290 

Arsenic 291 

Silver 296 

Gold 299 

Mercury 301 

Platinum 307 

Palladium 311 

Rhodium 312 

Iridium 312 

Ruthenium , -. 314 

Osmium 314 



PART III. 
ORGANIC CHEMISTRY. 

introduction 316 

Law of substitution 317 

tne ultimate analysis of organic bodies 320 

Empirical and rational formulae 329 

Determination of the density of the vapours of volatile liquids .... 330 
Saccharine and amylaceous substances, and the products of their 

alteration 333 

Cane and grape-sugars; sugar from ergot of rye; sugar of diabetes insipi- 
dus; liquorice-sugar; milk-sugar; mannite 333 

Starch; dextrin; starch from Iceland-moss ; inulin ; gum; pectin; lignin .. 337 

Oxalic and saccharic acids 341 

Xyloidin; pyroxylin; niucic acid 344 

Suberic, mellitic, rhodizonic, and croconic acids 345 

Fermentation of sugar. — Alcohol 345 

Lactic acid 349 

Ether, and ethyl-compounds 351 

Sulphovinic, phosphovinic, and oxalovinie acids 358 

Heavy oil of wine 362 

defiant gas; Dutch liquid; chlorides of carbon 362 



CONTENTS. XVII 

PAGE 

Ethionic and isethionic acids 365 

Chloral, &c 366 

Mercaptan ; xanthic acid 367 

Aldehyde; aldehydic acid; acetal 309 

Acetic acid 371 

Chloracetic acid 375 

Acetone 376 

Kakodyl ... 377 

Substances more oe less allied to alcohol. 

Wood-spirit; methyl-compounds 3S1 

Sulphomethylic acid 384 

Formic acid; chloroform 385 

Formomethylal ; methyl-mercaptan ,.... 387 

Potato-oil and its derivatives 388 

Sulphamylic acid; valerianic acid 390 

Chlorovalerisic and chlorovalerosic acids , 393 

Fusel-oil from grain-spirit; general view of the alcohols 393 

Bitter-almond-oil and its products; benzoyl-compounds 396 

Benzoic-acid ; sulphohenzoic acid; benzone and benzol 396 

Sulphobenzide and hyposulphobenzic acid 398 

Nitrobenzol, azobenzol, &c 399 

Formobenzoic acid; hydrobenzamide ; benzoin; benzile; benzilic acid; 

benzimide, &c 400 

Hippuric acid 402 

Homologues of benzoyl-series 403 

Salicin; salicyl and its compounds 403 

Chlorosamide. — Phloridzin. — Cumarin 405 

Cinnamyl and its compounds ; cinnamic acid ; chloro-cinnose 407 

Vegetable acids. 

Tartaric acid 410 

Racemic acid 413 

Citric acid 413 

Aconitic or equisetic acid 414 

Malic acid 414 

Fumaric and maleic acids 416 

Tannic and gallic acids , 416 

AZOTIZED ORGANIC PRINCIPLES OF SIMPLE CONSTITUTION. 

Cyanogen; paracyanogen ; hydrocyanic acid 420 

Amygdalin; amygdalic acid 423 

Metallic cyanides 424 

Cyanic,, cyanuric, and fulminic acids 426 

Chlorides, &c, of cvanogen 429 

2* 



XVJU CONTENTS. 

PAGE 

Ferro- and Arrricyanogen, and their compounds; Prussian blue 430 

Cobaltocyanogen ; nitroprussides 433 

Sulphocyanogen, and its compounds; selenocyanogen ; rnelam; melamine; 

ammeline; ammelide , 434 

Urea, and uric acid 436 

Allantoin ; alloxan ; alloxanic acid ; mesoxalic acid ; mykomelinic acid ; 

parabanic acid ; oxaluric acid ; tbionuric acid ; uramile ; alloxantin ; 

murexide; murexan 438 

Xantbic and cystic oxides 443 

The vegeto-alkalis, and allied bodies. 

Morphine, and its salts 444 

Narcotine ; opianic and hemipinic acids ; cotarnine 445 

Codeine; thebaine ; pseudo-morphine; narceine ; meconine 446 

Meconic acid 446 

Cinehonine and quinine; quinoidine 447 

Kinic acid; kinone; hydrokinone 448 

Strychnine and brucine ; veratrine . 449 

Conicine; nicotine; sparteine; harmaline; harmine; caffeine or theine; 

theobromine; berberine ; piperine; hyoscyamine; atropine; solanine; 

aconitine; delphinine; emetine; curarine 450 

Gentianln; populin; daphnin ; hesperidin ; elaterin ; antiarin ; picrotoxin ; 

asparagin; santonin 451 

Organic bases of artificial origin. 

Bases of the ethyl-series. — Ethylamine ; biethylamine ; triethylamine ; 

oxide of tetrethyl-ammonium 455 

Bases of the methyl-series. — Methylamine; bimethylamine; trimethyla- 

mine; oxide of tetramethyl-ammonium 457 

Bases of the amyl-series. — Amylamine ; biamylamine ; triamylamine ; 

oxide of tetramyl-ammonium 458 

Bases of the phenyl-series. — Aniline; chloraniline; nitraniline; cyaniline; 

melaniline , 459 

Bases homologous to aniline. — Toluidine ; xylidine; cumidine. Naphthali- 

tline; chloronicine 4G2 

Mixed bases. — Ethylaniline; biethylaniline ; oxide of triethylamyl-ammo- 

nium ; biethylamylamine ; oxide of methylobiethylamyl-ammonium ; 

methylethylamylamine; ethylamylaniline ; oxide of methyl-ethyl-amylo- 

phenyl-ammonium 463 

Bases of uncertain constitution. 

Chinoline 464 

Kyanol; leucol; picolinc 465 

Petinine 465 

Furfurine 465 



CONTENTS. XIX 

PAGE 

Fucusine ; amarine; thiosinnamine . 466 

Thialdinc ; alanine 467 

Phosphorus-bases 468 

Antimony-bases r 469 

Organic colouring principles. 

Indigo; white indigo; sulphindylic acid 470 

Isatin; anilie and picric acids ; chrysanilic and an thranilic acids 471 

Litmus — lecanorin; orcin ; orcein, &c 474 

Cochineal, madder, dye-woods, &c 477 

Chrysammic, chrysolepic, and styphnic acids 479 

Oils and fats. 

Fixed oils ; margarin, stearin, and olein ; saponification, and its products ; 

glycerin 480 

Palm and cocoa-oils. — Elaidin and elaidic acid 483 

Suberic, succinic, and sebacic acids 484 

Butter. — Butyric, caproic, caprylic, and capric acids 485 

Wax; spermaceti; cholesterin ; cantharidin 486 

Acrolein; acrylic acid 487 

Products of the action of acids on fats 487 

Castor-oil; caprylic alcohol 488 

Volatile oils. — Oils of turpentin, lemons, aniseed, cumin, cedar, gaultheria, 

valerian, peppermint, lavender, rosemary, orange-flowers, rose-petals 488 

Camphor; camphoric acid 492 

Oils of mustard, garlic, onions, &c 492 

Resins. — Caoutchouc 493 

Balsams. — Toluol, styrol 494 

Components of the animal body. 

Albumin, fibrin, and casein; protein 49g 

Gelatin and chondrin 500 

Kreatin and kreatinine 502 

Composition of the blood ; respiration; animal heat 503 

Chyle; lymph; mucus; pus 507 

Milk; bile; urine; urinary calculi 508 

Nervous substance ; membranous tissue ; bones 516 

The function of nutrition in the vegetable and animal kingdoms 513 

Products of the destructive distillation, and slow putrefactive 
change of organic matter. 

Substances obtained from tar. — Paraffin; eupione; picamar; kapnomor; 
eedriret ; kreosote; chrysen and pyren „ 523 



XX CONTENTS. 

PAOB 

Coal-oil. — Carbolic acid (hydrate of oxide of phenyl) 526 

Naphthalin and paranaphthalin 529 

Petroleum, naphtha, and other allied substances. 530 

&.JPPENDIX. 

Hydrometer tables. — Table of the tension of the vapour of water at differ- 
ent temperatures. — Table of the proportion of real alcohol in spirits 
of different densities. — Analyses of the mineral waters of Germany. — 
Table of weights and measures 533 



LIST OF ILLUSTRATIONS 

BY WOOD-CUTS. 



Fig. Pa?o 

1 Specific-gravity bottle ■-.. 28 

2 " « 29 

3 « " 29 

4 " * 29 

5 " " 30 

6 « " beads , 31 

7 Hydrometer 32 

8 Urinometer 32 

9 Specific gravity 33 

10 Elasticity of gases 34 

11 Single air-pump 35 

12 Double " 36 

13 Improved" 36 

14 " * 37 

15 Barometer 38 

16 " 39 

17 « 40 

18 Expansion of solids 41 

19 " liquids 41 

20 " gases 41 

21 Differential thermometer 43 

22 " " 43 

23 Difference of expansion in metals 44 

24 Gridiron pendulum 44 

25 Mercury " 45 

26 Compensation balance 45 

27 Daniell's pyrometer 45 

28 Expansion of mercury 47 

29 Atmospheric currents 50 

30 " " 50 

31 « « 51 

32 Boiling paradox 55 

33 Steam-bath 57 

34 Steam-engine 57 

35 Distillation 58 

36 Liebig's condenser 59 

37 Tension of vapour 59 

38 " " CO 

39 Wet-bulb hygrometer 62 

(xxi) 



:~° 



XX11 LIST OF ILLUSTRATIONS. 

Fig. 

40 Condensation of gases 63 

41 Thilorier's apparatus 64 

42 Cold by evaporation 65 

43 "Wollaston's cryophorus 65 

44 Daniell's hygrometer 65 

45 Reflection of light 72 

46 Refraction of light 72 

47 " " 72 

48 « " 73 

49 Spectrum 74 

50 " 74 

51 Polarization of light 75 

52 « « 76 

53 " " 76 

54 Reflection of heat 79 

55 " " 80 

m 

56 Effects of electrical current on the magnetic needle 82 

57 " " " " 82 

58 Current produced by heat 83 

59 Melloni's instrument for measuring transmitted heat 83 

60 Magnetic polarity 87 

61 " " 87 

62 Electro repulsion 93 

63 Electroscope S3 

64 Electric polarity 93 

65 Electrical machine 95 

66 " " plate 95 

67 Leyden jar 96 

68 Electrophorus 97 

69 Volta'spile 98 

70 Crown of cups 98 

71 Cruikshank's trough 99 

72 Effect of electrical current on the magnetic needle 100 

73 Astatic needle 101 

74 Magnetism developed by the electrical current 101 

75 " " " " 102 

76 Electro-magnet 102 

77 Apparatus for oxygen 105 

78 Hydro-pneumatic trough 106 

79 Transferring gases 107 

80 Pepy's hydro-pneumatic apparatus 107 

81 Apparatus for hydrogen Ill 

82 Levity of hydrogen HI 

83 Diffusion of gases 112 

84 Daniell's safety-jet 113 

85 Musical sounds by hydrogen 114 

86 CatalyVc effect of platinum 115 



LIST OF ILLUSTRATIONS. XX1U 

Fig. Page 

87 Decomposition of water ■ 116' 

88 Eudiometer of Cavendish 316 

S9 Analysis of water .-. 116 

90 Preparation of nitrogen 120 

91 Analysis of air 121 

92 lire's eudiometer 122 

93 Preparation of nitric acid 123 

9i " protoxide of nitrogen 125 

95 Crystalline form of carbon 127 

96 " " " 127 

97 " " " 127 

98 " " " 127 

99 Preparation of carbonic acid 129 

100 Mode of forming caoutchouc connecting-tubes 129 

101 Crystalline form of sulphur 131 

102 Crystals of sulphur m 131 

103 Crystalline form of sulphur 131 

104 Preparation of phosphorus 137 

105 " chlorine 139 

106 " hydrochloric acid . 142 

107 Safety-tube 143 

108 Combustible under water 145 

109 Preparation of hydriodic acid 147 

110 " silica « 150 

111 Blast furnace 157 

112 Reverberatory furnace 157 

113 Structure of flame 15S 

114 Mouth blowpipe 159 

115 Structure of blowpipe flame 159 

116 Argand spirit-lamp 159 

117 Common " 159 

118 Mitchell's " 16f. 

119 Gas " 16C 

120 Davy's safe " 161 

121 Hemming's safety-jet 161 

122 Effect of metallic coil 161 

123 Apparatus for sulphuretted hydrogen 164 

124 Multiple proportions 181 

125 Water in its usual state 1SS 

126 " undergoing electrolysis 189 

127 Voltameter 190 

128 Decomposition without contact of metals 191 

129 Wollaston's voltaic battery 193 

130 Daniell's constant " 193 

131 Grove's '• " 194 

132 Electrotype 195 

133 Lead-tree I9a 



XXIV LIST OF ILLUSTRATIONS. 

Fig. Page 

134 Wire-drawing 19S 

J35 Wollaston's goniometer 203 

136 Reflecting " 204 

137 " " principles of 205 

138 Crystals, regular system 206 

139 " regular prismatic system 206 

110 " right prismatic system 207 

141 " oblique prismatic 6ystem 207 

142 " doubly oblique prismatic system .. 203 

143 Crystals, rbombohedral sj'stem 208 

144 " passage of cube to octahedron 209 

145 " " " octahedron to tetrahedron 209 

146 Alkalimeter 227 

147 Apparatus fov determining carbonic acid 228 

148 " " " " « 229 

149 Iron manufacture. Blast-furnace ; , 264 

150 Crystals of arsenious acid 293 

151 Subliming tube for arsenic 294 

152 Marsh's test 295 

153 Weighing tube » 321 

154 Combustion 321 

155 Chauffer 322 

156 Water tube 322 

157 Carbonic acid bulbs 322 

158 Apparatus complete 323 

159 Bulb for liquids 324 

160 Comparative determination of nitrogen 325 

161 Pipette 325 

162 Absolute estimation of nitrogen 326 

163 Varentrap's and Will's method 327 

164 Determination of the density of vapours 330 

165 Starch granules 338 

166 Preparation of ether 361 

167 " defiant gas. 363 

163 " Dutch liquid 363 

169 Catalysis 371 

L70 Preparation of kakodyle 379 

171 " benzoic acid , 397 

172 " tannic acid 417 

173 Uric acid crystals 43S 

174 Blood globules 504 

UT5 Pus " 508 

176 Milk " 508 

177 Trommer's test 514 

178 Uric acid calculus 515 

179 Urate of ammonia calculus 515 

J80 Fusible calculus 516 

181 Mulberry calculus 516 



MANUAL OF CHEMISTRY, 



INTRODUCTION. 

The Science of Chemistry has for its object the study of the nature and 
properties of all the materials which enter into the composition or structure 
of the earth, the sea, and the air, and of the various organized or living be- 
ings which inhabit these latter. Every object accessible to man, or which 
may be handled and examined, is thus embraced by the wide circle of 
Chemical Science. 

The highest efforts of Chemistry are constantly directed to the discovery 
of the general laws or rules which regulate the formation of chemical com- 
pounds, and determine the action of one substance upon another. These 
laws are deduced from careful observation and comparison of the properties 
and relations of vast numbers of individual substances; — and by this method 
alone. The science is entirely experimental, and all its conclusions the re- 
sults of skilful and systematic experimental investigation. 

The applications of the discoveries of Chemistry to the arts of life, and 
to the relief of human suffering in disease, are, in the present state of the 
science, both very numerous and very important, and encourage the hope 
of still greater benefits from more extended knowledge than that now 
enjoyed. 

In ordinary scientific speech the term chemical is applied to changes which 
permanently affect the properties or characters of bodies, in opposition to 
effects termed physical, which are not attended by such consequences. 
Changes of decomposition or combination are thus easily distinguished from 
those temporarily brought about by heat, electricity, magnetism, and the 
attractive forces, whose laws and effects lie within the province of Physics 
or Natural Philosophy. 

Nearly all the objects presented by the visible world are of a compound 
nature, being chemical compounds, or variously disposed mixtures of chem- 
3 (25) 



26 INTRODUCTION. 

ical compounds, capable of being resolved into simpler forms of matter. 
Thus, a piece of limestone or marble by the application of a red-heat is de- 
composed into quicklime and a gaseous body, carbonic acid. Both lime 
and carbonic acid are in their turn susceptible of decomposition, the first 
into a metal, calcium, and oxygen, and the second into carbon and oxygen. 
For this purpose, however, simple heat does not suffice, the resolution of 
these substances into their components demanding the exertion of a high 
degree of chemical energy. Beyond this second step of decomposition the 
efforts of Chemistry have hitherto been found to fail, and the three bodies, 
calcium, carbon, and oxygen, having resisted all attempts to resolve them 
into simpler forms of matter, are accordingly admitted into the list of ele- 
ments; — not from any belief in their real oneness of nature, but from the 
absence of any evidence that they contain more than one description of 
matter. 

The partial study of certain branches of Physical Science, as the physical 
constitution of gases, the chief phenomena of heat and electricity, and a 
few other subjects, forms such an indispensable introduction to Chemistry 
itself, that it is never omitted in the usual courses of oral instruction. A 
sketch of these subjects is, in accordance with these views, placed at the 
commencement of the present volume. 



PAET I.— PHYSICS. 

OF DENSITY AND SPECIFIC GRAVITY. 

It is of great importance in the outset to understand clearly what is meant 
by the terms density and specific gravity. By the density of a body is meant 
its mass, or quantity of matter, compared with the mass or quantity of matter 
of an equal volume of some standard body, arbitrarily chosen. Specific 
gravity denotes the weight of a body, as compared with the weight of an 
equal bulk, or volume, of the standard body, which is reckoned as unity. 1 
In all cases of solids and liquids this standard of unity is pure water at the 
temperature of CO Fahr. (15°-5C). Anything else might have been chosen; 
there is nothing in water to render its adoption for the purpose mentioned 
indispensable ; it is simply taken for the sake of convenience, being always 
at hand, and easily obtained in a state of perfect purity. The ordinary ex- 
pression of specific weight, therefore, is a number expressing how many 
times the weight of an equal bulk of water is contained in the weight of 
the substance spoken of. If, for example, we say that concentrated oil of 
vitriol has a specific gravity equal to 1-85, or that perfectly pure alcohol has 
a density of 0-794 at 60°, we mean that equal bulks of these two liquids 
and of distilled water possess weights in the proportion of the num- 
bers 1-85, 0-794, and 1 ; or 1850, 794, and 1000. It is necessary to be par- 
ticular abotit the temperature ; for, as will be hereafter shown, liquids are 
extremely expansible by heat ; otherwise, a constant bulk of the same liquid 
will not retain a constant weight. It will be proper to begin with the de- 
scription of the mode in which the specific gravity of liquids is determined; 
this is the simplest case, and the one which best illustrates the general 
principle. 

In order to obtain at pleasure the specific gravity of any particular liquid 
compared with that of water, it is only requisite to weigh equal bulks at the 
standard temperature, and then divide the weight of the liquid by the weight 
of the water ; the quotient will of course be greater or less than unity, as 
the liquor experimented on is heavier or lighter than water. Now, to weigh 
equal bulks of two fluids, the simplest and best method is clearly to weigh 
them in succession in the same vessel, taking care that it is equally full on 
both occasions, a condition very easy of fulfilment. 

A thin glass bottle, or flask, with a narrow neck, is procured, of the figure 
represented on the next page, (fig. 1), and of such capacity as to contain, 
when filled to about half-way up the neck, exactly 1000 grains of distilled 
Water at 60° (15° -5C). Such a flask is readily procured from any one of the 
Italian artificers, to be found in every large town, who manufacture cheap 
thermometers for sale. A counterpoise of the exact weight of the empty 

1 In other words, density means comparative mass, and specific gravity comparative weight. 
These expressions, although really relating to distinct things, are often used quite indiffe- 
rently in chemical writings, and without practical inconvenience, since mays and weight are 
directly proportional to each other. 

(27) 



28 



DENSITY AND SPECIFIC GRAVITY. 



Fig. 1. 




Lottie is made from a tit of brass, an old weight, 
or something of the kind, and carefully adjusted 
by filing : an easy task. The bottle is then grad- 
uated, by introducing water at 60°, until it ex- 
actly balances the 1000-grain weight and counter- 
poise in the opposite scale ; the height at which 
the water stands in the neck is marked by a 
scratch, and the instrument is complete for use. 
The liquid to be examined is brought to the tem- 
perature of 60°, and with it the bottle is filled up 
to the mark before mentioned ; it is then weighed, 
the counterpoise being used as before, and the 
specific gravity directly ascertained. 

A watery liquid in a narrow glass tube always 
presents a curved surface from the molecular ac- 
tion of the glass, the concavity being upwards. It 
is better, on this account, in graduating the bottle, 
to make two scratches as represented in the draw- 
ing, one at the top and the other at the bottom of 
the curve : this prevents any future mistake. The 
bjarks are easily made by a fine, sharp, three-square file, the hard point of 
•ft Inch, also, it may be observed, answers perfectly well for writing upon 
glass, in the absence of a proper diamond-pencil. 

The specific-gravity bottle above described differs from those commonly 
made for sale by the instrument-makers. These latter are constructed with 
a perforated stopper, so arranged that when the bottle is quite filled, the 
stopper put in its place, and the excess of liquid which flows through the 
hole wiped from the outside, a constant measure is always had. There are 
inconveniences attending the use of the stopper which lead to a preference 
of the open bottle with merely a mark on the neck, even when very volatile 
liquids are experimented with. 

It will be quite obvious that the adoption of a flask holding exactly 1000 
grains of water has no other object than to save the trouble of a very trifling 
calculation ; any other quantity would answer just as well, and, in fact, the 
experimental chemist is often compelled to use a bottle of much smaller di- 
mensions, from scarcity of the liquid to be examined. The shape is also in 
reality of little moment ; any light phial with a narrow neck may be em- 
ployed, not quite so conveniently perhaps, as a specific-gravity bottle. 

The determination of the specific gravity of a solid is also an operation of 

great facility, although the principle is not so obvious. As it would be 

impossible to put in practice a direct method like that indicated for liquids, 

recourse is had to another plan. The celebrated theorem of Archimedes 

affords a solution of the difficulty. This theorem may be thus expressed: — 

"When a solid is immersed in a fluid, it loses a portion of its weight ; 

and this portion is equal to the weight of the fluid which it displaces: 

that is, to the weight of its own bulk of that fluid. 

It is easy to give experimental proof of this very important proposition, 

as well as to establish it by reasoning. The drawing (fig. 2) represents a 

little apparatus for the former purpose. This consists of a thin cylindrical 

vessel of brass, into the interior of which fits very accurately a solid cylinder 

of the same metal, thus exactly filling it. When the cylinder is suspended 

beneath the bucket, as seen in the sketch, the whole hung from the arm of 

a balance and counterpoised, and then the cylinder itself immersed in water, 

it will be found to have lost a certain weight ; and that this loss is precisely 

equal to the weight of an equal bulk of water, may then be proved by filling 



DENSITY AND SPECIFIC GRAVITY. 



29 



tie Ducket to the brim, whereupon the equilibrium 
ffiil be restored. 

The consideration of the great hydrostatic law of 
fluid pressure easily proves the truth of the principle 
laid down. Let the reader figure to himself a vessel 
of water, having immersed in it a solid cylindrical or 
rectangular body, and so adjusted with respect to 
density, that it shall float indifferently in any part 
beneath the surface (fig. 3). 

N ow the law of fluid pressure is to this effect : — 
The pressure exerted by a fluid upon the containing 
vessel, or upon anything plunged beneath its surface, 
depends, first, upon the density of that fluid, and, 
secondly, upon the perpendicular height of the col- 
umn. It is independent of the form and lateral 
dimensions of the vessel or immersed body. More- 
over, owing to the peculiar physical constitution of 
fluids, this pressure is exerted equally in every di- 
rection, upwards, downwards, and laterally, with 
equal force. 

The floating body is in a state of equilibrium ; 
therefore the pressure downwards caused by its gravi- 
tation must be exactly compensated by the upward 
transmitted pressure of the column of water a, b. 

But this pressure downwards is obviously equal to 
the weight of an equal quantity of water, since the 
body of necessity displaces its own bulk — 

Hence, the weight lost, or supported by the water, 
; s the weight of a volume of water equal to that of 
the body immersed. 

Whatever be the density of the substance it will be 
buoyed up to this amount : in the case supposed, 
the buoyancy is equal to the whole weight of the 
body, which is thus, while in the water, reduced to 
nothing. 

A little reflection will show that the same reasoning 
may be applied to a body of irregular form ; besides, 
a solid of any figure may be divided by the imagina- 
tion, into a multitude of little perpendicular prisms, 
or cylinders, to each of which the argument may be 
applied. What is true of each individually, must 
necessarily be true of the whole together. 

This is the fundamental principle; its application 
is made in the following manner : — Let it be required, 
for example, to know the specific gravity of a body 
of extremely irregular form, as a small group of rock- 
crystals : the first part of the operation consists in 
determining its absolute weight, or, more correctly 
speaking, its weight in air; it is next suspended from 
the balance-pan by a fine horse-hair, immersed com- 
pletely (fig. 4) in pure water at GO (15°-5C), and 
again weighed. It now weighs less, the difference 
being the weight of the water it displaces, that is, the 
weight of an equal bulk. This being known, nothing 
more is required than to find, by division, how many 
8* 



Tig. 2. 





Fisj. 4. 





80 DENSITY AND SPECIFIC GRAVITY. 

times the latter number is contained in the former; the quotient 'will be the 
density, water being taken = 1. For example: — ■ 

The quartz-crystals weigh in air 293-7 grains. 

"When immersed in water, they weigh 180-1 

Difference being the weight of an equal volume of water ... 113-6 
293-7 
I • ■!■->. A = 2-58, the specific gravity required. 

The arbitrary rule is generally thus written : "Divide the weight in air 

by the loss of weight in water, and the quotient will be the specific gravity." 

In reality, it is not the weight in air which is required, but the weight the 

body would have in empty space : the error introduced, 

Fi S- 5 - namely, the weight of an equal bulk of air, is so trifling that 

it is usually neglected. 

Sometimes the body to be examined is lighter than water, 
and floats. In this case it is first weighed and afterwards 
attached to a piece of metal (fig. 5), heavy enough to sink 
it, and suspended from the balance. The whole is then ex- 
actly weighed, immersed in water, and again weighed. The 
difference between the two weighings gives the weight of a 
quantity of water equal in bulk to both together. The light 
substance is then detached, and the same operation of weigh- 
ing in air, and again in water, repeated on the piece of metal. 
These data give the means of finding the specific gravity, as 
will be at once seen by the following example : — 

Light substance (a piece of wax) weighs in air 133-7 grains. 

Attached to a piece of brass, the whole now weighs 183-7 

Immersed in water, the system weighs 38-8 

Weight of water equal in bulk to brass and wax 144-9 

Weight of brass in air 50-0 

Weight of brass in water 44-4 

Weight of equal bulk of water 5-6 

Bulk of water equal to wax and brass 144-9 

Bulk of water equal to brass alone 5-6 

Bulk of water equal to wax alone 139-3 

133-7 

139^3 = °' 9598 ' 

In all such experiments, it is necessary to pay attention to the temperature 
and purity of the water, and to remove with great care all adhering air- 
bubbles ; otherwise a false result will be obtained. 

Other cases require mention in 'which these operations must be modified 
to meet particular difficulties. One of these happens when the substance is 
dissolved or acted upon by water. This difficulty is easily conquered by 
substituting some other liquid of known density which experience shows is 
without action. Alcohol or oil of turpentine may generally be used when 
water is inadmissible. Suppose, for instance, the specific gravity of crys- 
tallized sugar is required, we proceed in the following way : — The specific 
gravity of the oil of turpentine is first carefully determined ; let it be 0-87 ; 



DENSITY AND SPECIFIC GRAVITY. 31 

the sugar is next weighed in the air, then suspended by a horse-hair, and 
weighed in the oil ; the difference is the weight of an equal bulk of the latter ; 
a simple calculation gives the weight of a corresponding volume of water : — 

Weight of sugar in air 400 grains. 

Weight of sugar in oil of turpentine 182-5 

Weight of equal bulk of oil of turpentine 217-5 

87 : 100 = 217-5 : 250, 
the weight of an equal bulk of water : hence the specific gravity of the sugar, 

!5° = l-6. 
250 

The substance to be examined may be in small fragments, or powder. 
Here the operation is also very simple. A bottle holding a known weight 
of water is taken ; the specific-gravity bottle already described answers per- 
fectly well. A convenient quantity of the substance is next carefully weighed 
out, and introduced into the bottle, which is then filled up to the mark on 
the neck with distilled water. It is clear that the vessel now contains less 
water by a quantity equal to the bulk of the powder than if it were filled in 
the usual manner. It is, lastly, weighed. In the subjoined experiment 
emery powder was tried. 

The bottle held, of water 1000 grains. 

The substance introduced weighed 100 

Weight of the whole, had no water been displaced 1100 

The observed weight is, however, only 1070 

• Hence water displaced, equal in bulk to the powder 80 

100 
oTT = 3-333 specific gravity. 

By this method the specific gravities of metals in powder, metallic oxides, 
and other compounds, and salts of all descriptions, may be determined with 
great ease. Oil of turpentine may be used with most soluble salts. The 
crystals should be crushed or roughly powdered to avoid errors arising from 
cavities in their substance. 

The theorem of Archimedes affords the key to the general doctrine of the 
equilibrium of floating bodies, of which an application is made in the common 
hydrometer, — an instrument for finding the specific gravities of liquids in a 
very easy and expeditious manner. 

When a solid body is placed upon the surface of a fluid specifically heavier 
than itself, it sinks down until it displaces a quantity of fluid equal to its 
own weight, at which point it floats. Thus, in the case of a substance floating 
in water, whose specific weight is one-half that of the fluid, the position of 
equilibrium will involve the immersion of exactly one-half of 
the body, inasmuch as its whole weight is counterpoised by a Fi S- 

quantity of water equal to half its volume. If the same body 
were put into a fluid of one-half the specific gravity of water, / p,~ 
if such could be found, then it would sink beneath the surface, 
and remain indifferently in any part. A floating body of known 
specific gravity may thus be used as an indicator of the spe- 
cific gravity of a fluid. In this manner little glass beads (fig. 6) a/,% 
of known specific gravities are sometimes employed in the arts 
to ascertain in a rude manner the specific gravity of liquids ; 




32 



DENSITY AND SPECIFIC GRAVITY. 



Kg. 7. 



the one that floats indifferently beneath the surface, •without either sinking 
or rising, has of course the same specific gravity as the liquid itself; this is 
pointed out by the number marked upon the bead. 

The hydrometer (fig. 7) in general use consists 
of a floating vessel of thin metal or glass, having 
a "weight beneath to maintain it in an upright 
position, and a stem above bearing a divided 
scale. The use of the instrument is very simple. 
The liquid to be tried is put into a small narrow 
jar, and the instrument floated in it. It is obvious 
that the denser the liquid, the higher will the 
hydrometer float, because a smaller displacement 
of fluid will counterbalance its weight. For the 
same reason, in a liquid of less density, it sinks 
deeper. The hydrometer comes to rest almost 
immediately, and then the mark on the stem at the 
fluid-level may be read off. 

Very extensive use is made of instruments of 
this kind in the arts ; these sometimes bear dif- 
ferent names, according to the kind of liquid for 
•which they are intended ; but the principle is the 
same in all. The graduation is very commonly 
arbitrary, two or three different scales being un- 
fortunately used. These may be sometimes re- 
duced, however, to the true numbers expressing 
the specific gravity by the aid of tables of com- 
parison drawn up for the purpose. 

A very convenient and useful instrument in the 
shape of a small hydrometer (fig. 8) for taking the 
specific gravity of urine, has lately been put into 
the hands of the physician ; x it may be packed into 
a pocket-case, with a little jar and a thermomeier, 
and is always ready for use. 1 

The determination of the specific gravity of 
gases and vapours of volatile liquids is a problem 
of very great practical importance to the chemist; 
the theory of the operation is as simple as when 
liquids themselves are concerned, but the pro- 
cesses are much more delicate, and involve be- 
sides certain corrections for differences of tem- 
perature and pressure, founded on principles yet 
to be discussed. It will be proper to defer the 
consideration of these matters for the present. 
The method of determining the specific gravity 
of a gas will be found described under the head of 




Pig. 8. 




' Ihia and other instruments described or figured in the course of the work, may he had 
of fir. Newman, 122 Regent Street, upon the excellence of whose workmanship reliance may 
bo safely placed. 

a The graduation of the urinometer is such that each degree represents 1-1000, thus 
giving the actual specific gravity without calculation, for the number of <lQ;:vrc> on the 
scale cut by the surface of the liquid when this instrument is at rest, added to lnoo will 
epresent the density of the liquid. If, for example, the surface of the liquid coincide with 
^.'> on the scale, the specific gravity will be 1023, about the average density of healthy 
urine — h 1$ 



DENSITY AND SPECIFIC GRAVITY. 



33 



u Oxygen," and that of the vapour of a volatile liquid in the Introduction 
to Organic Chemistry. 1 



— = •836 the specific gravity required. — R. B. 




1 The mode of determining the specific gravity of a liquid by means of a 
solid has been omitted in the text. It results from the theorem of Ar- 
chimedes, that if any solid be immersed in water and then in any other 
liquid, the loss of height sustained in each case will give the relative 
weights of equal bulks of the liquids, and on dividing the weight of the 
liquid by the weight of the water, the quotient will be the specific gravity 
of the liquid experimented on. For instance, let a piece of* glass rod be 
suspended from the balance-pan and exactly counterpoised, then immerse 
it in water and restore the equipoise by weights added to the pan to 
which the glass is suspended, the amount will give the loss of weighs by 
immersion or the weight of a bulk of water equal to that of the Tod. 
Now wipe the glass dry, and having removed the additional weights, 
immerse it in the other liquid, and restore the equipoise as before, '.Lis 
latter weight is the weight of a bulk of the liquid equal to that of the 
water. The latter divided by the former gives the specific gravity. x»„j: 
example: — 

The glass rod loses by immersion in water 171 f* ^^ 

The glass rod loses by immersion in alcohol 143 



u 



PHYSICAL CONSTITUTION 



OF THE PHYSICAL CONSTITUTION OF THE ATMOSPHERE, AND 
OF GASES IN GENERAL. 



Fig. 10. 



It requires some little abstraction of mind to realize completely the singu- 
lar condition in which all things at the surface of the earth exist. We live 
at the bottom of an immense ocean of gaseous matter, "which envelopes 
everything, and presses upon everything with a force which appears, at first 
sight, perfectly incredible, but whose actual amount admits of easy proof. 

Gravity being, so far as is known, common to all matter, it is natural to 
expect that gases, being material substances, should be acted upon by the 
earth's attraction, as well as solids and liquids. This is really the case, and 
the result is the weight or pressure of the atmosphere, which is nothing 
more than the effect of the attraction of the earth on the particles of air. 

Before describing the leading phenomena of the atmospheric pressure, it 
is necessary to notice one very remarkable feature in the physical constitu- 
tion of gases, upon which depends the principle of an extremely valuable 
instrument, the air-pump. 

Gases are in the highest degree elastic ; the volume or space which a gas 
occupies depends upon the pressure exerted upon it. Let the reader imagine 
a cylinder, a, fig. 10, closed at the bottom, in 
which moves a piston, air-tight, so that no air 
can escape between the piston and the cylinder. 
Suppose now the piston be pressed downwards 
with a certain force; the air beneath it will be 
compressed into a smaller bulk, the amount of 
this compression depending on the force ap- 
plied ; if the power be sufficient, the bulk of 
the gas may be thus diminished to one hun- 
dredth part or less. When the pressure is re- 
moved, the elasticity or teiision, as it is called, 
of the included air or gas, will immediately 
force up the piston until it arrives at its first 
position. 

Again, take b, fig. 10, and suppose the piston to 
stand about the middle of the cylinder, having 
air beneath in its usual state. If the piston 
be now drawn upwards, the air below will ex- 
pand, so as to fill completely the enclosed 
space, and this to an apparently unlimited ex- 
tent. A volume of air which under ordinary circumstances occupies the 
hulk of a cubic inch, might, by the removal of the pressure upon it, be 
made to expand to the capacity of a whole room, while a renewal of the 
former pressure would be attended by a shrinking down of the air to its 
former bulk. The smallest portion of gas introduced into a large exhausted 
vessel becomes at once diffused through the whole space, an equal quantity 
being present in every part; the vessel is full, although the gas is in a state 
of extreme teiruity. This power of expansion which air possesses may have, 
and probably has, in reality, a limit; but the limit is never reached in 






1 
Iff 

II 



OF THE A T 3IOSPUERE. oO 

practice. We are quite safe in the assumption, that, for ail purposes of 
experiment, however refined, air is perfectly elastic. 

It is usual to assign a reason for this indefinite expansibility by ascribing 
to the particles of material bodies, when in a gaseous state, a self-repulsive 
energy. This statement is commonly made somewhat in this manner: 
matter is under the influence of two opposite forces, one of which tends to 
draw the particles together, the other to separate them. By the preponde- 
rance of one or other of these forces, we have the three states called solid, 
liquid, and gaseous. When the particles of matter, in consequence of the 
direction and strength of their mutual attractions, possess only a very slight 
power of motion, a solid substance results ; when the forces are nearly 
balanced, we have a liquid, the particles of which in the interior of the 
mass are free to move, but yet to a certain extent are held together ; and, 
lastly, when the attractive power seems to be completely overcome by its 
antagonist, we have a gas or vapour. 

Various names are applied to these forces, and various ideas entertained 
concerning them ; the attractive forces bear the name of cohesion when they 
are exerted between particles of matter separated by a very small interval, 
and gravitation, when the distance is great. The repulsive principle is often 
thought to be identical with the principle of heat. 

He. 11. 




The ordinary air-pump, shown in section in fig. 11, consists essentially of 
& metal cylinder, in which moves a tightly-fitting piston, by the aid of its 
rod. The bottom of the cylinder communicates with the vessel to be ex- 
hausted, and is furnished with a valve opening upwards. A similar valve, 
also opening upwards, is fitted to the piston; these valves are made with 
slips of oiled silk. When the piston is raised from the bottom of the cy 
linder, the space left beneath it must be void of air, since the piston-valve 
opens only in one direction ; the air within the receiver having on that side 
nothing to oppose its elastic power but the weight of the little valve, lifts 
the latter, and escapes into the cylinder. So soon as the piston begins to 
descend, the lower valve closes, by its own weight, or by the transmitted 
pressure from above, and communication with the receiver is cut off. As 
the descent of the piston continues, the air included within the cylinder be- 



36 



PHYSICAL CONSTITUTION 



comes compressed, its elasticity is increased, and at length it forces 
the upper valve, and escapes into the atmosphere. In this manner, a cy- 
linder full of air is at every stroke of the pump removed from the receiver. 
During the descent of the piston, the upper valve remains open, and the 
lower closed, and the reverse during the opposite movement. 



Fig. 12. 




T?ig. 13. 



In practice, it is very convenient to have two such barrels or cylinders, 
arranged side by side, the piston-rods of which are formed 
into racks, having a pinion, or small-toothed wheel, be- 
tween them, moved by a winch. By this contrivance the 
operation of exhaustion is much facilitated and the labour 
lessened. The arrangement is shown in fig. 12. 

A simpler and far superior form of air-pump is thus 
constructed: the cylinder, which may be of large dimen- 
sions, is furnished with an accurately-fitted solid piston, 
the rod of which moves, air-tight, through a contrivance 
called a stuffing-box, at the top of the cylinder, where also 
the only valve essential to the apparatus is to be found ; the 
latter is a solid conical plug of metal, shown at a in the 
figure, kept tight by the oil contained in the chamber into 
which it opens. The communication with the vessel to be 
exhausted is made by a tube which enters the cylinder a 
little above the bottom. The action is the following : let 
the piston be supposed in the act of rising from the bottom 
of the cylinder ; as soon as it passes the mouth of the tube 
i, all communication is stopped between the air above the 
piston and the vessel to be exhausted ; the enclosed air 
suffers compression, until it acquires sufficient elasticity 
to lift the metal valve and escape by bubbling through the 
oil. When the piston makes its descent, and this valve 



M\ 

a. 

ill mil 





OF THE ATMOSPHERE. 



Fig. 14. 



closes, a vacuum is left in the tipper part of the cylinder, into which the air 
of the receiver rushes so soon as the piston has passed below the orifice of 
the connecting tube. 

In the silk-valved air-pump, exhaustion ceases when the elasticity of the 
air in the receiver becomes too feeble to raise the valve ; in that last 
described, the exhaustion may, on the contrary, be carried to an indefinite 
extent, without, however, under the most favourable circumstances, be- 
coming complete. The conical valve is made to project a little below the 
cover of the cylinder, so as to be forced up by the piston when the latter 
reaches the top of the cylinder ; the oil then enters and displaces any air 
that may be lurking in the cavity. 

It is a great improvement to the machine to supply the piston with a 
relief-valve opening upwards ; this may 
also be of metal, and contained within the 
body of the piston. Its use is to avoid 
the momentary condensation of the air in 
the receiver when the piston descends. 
The pump is worked by a lever in the 
manner represented in fig. 14. 

To return to the atmosphere. Air pos- 
sesses weight : a light flask or globe of 
glass, furnished with a stop-cock and ex- 
hausted by the air-pump, weighs consi- 
derably less than when full of air. If the 
capacity of the vessel be equal to 100 
cubic inches, this difference may amount 
to nearly 30 grains. 

The mere fact of the pressure of the 
atmosphere may be demonstrated by se- 
curely tying a piece of bladder over the 
mouth of an open glass receiver, and then 
exhausting the air from befteath it ; the 
bladder will become more and more con- 
cave, until it suddenly breaks. A thin 
square glass bottle, or a large air-tight 
tin box, may be crushed by withdrawing 
the support of the air in the inside. 
Steam-boilers have been often destroyed 
in this manner by collapse, in conse- 
quence of the accidental formation of a 
partial vacuum within. 

After what has been said on the subject 
of fluid pressure, it will scarcely be ne- 
cessary to observe that the law of equality 
of pressure in all directions also holds 
good in the case of the atmosphere. The 
perfect mobility of the particles of air 
permits the transmission of the force ge- 
nerated by their gravity. The sides and 
bottom of an exhausted vessel are pressed 
upon with as much force as the top. 

If a glass tube of considerable length 
could be perfectly exhausted of air, and 
then held in an upright position, with one 
of its ends dipping into a vessel of liquid, 




PHYSIC A L CONSTITUTION 



Fi* .15. tlie latter, on being allowed access to the tube, -would rise in 

its interior until the weight of the column balanced the pres- 
sure of the air upon the surface of the liquid. Now if the 
density of this liquid were known, and the height and area 
of the column measured, means would be furnished for ex- 
actly estimating the amount of pressure exerted by the atmo- 
sphere. Such an instrument is the barometer: a straight 
glass tube is taken, about 86 inches in length, and sealed by 
the blow-pipe flame at one extremity; it is then filled with 
clean, dry mercuiy, care being taken to displace all air- 
bubbles, the open end stopped with a finger, and the tube in- 
verted in a basin of mercuiy. On removing the finger, tha 
fluid sinks away from the top of the tube, until it stands at 
the height of about 80 inches above the level of that in the 
basin. Here it remains supported by, and balancing the at- 
mospheric pressure, the space above the mercury in the tube 
being of necessity empty. 

The pressure of the atmosphere is thus seen to be capable 
of sustaining a column of mercury 30 inches in height, or 
thereabouts ; now such a column, having an area of one inch, 
weighs between 14 and 15 pounds, consequently such must 
be the amount of the pressure exerted upon every square 
inch of the surface of the earth, and of the objects situated 
thereon, at least near the level of the sea. This enormous 
force is borne without inconvenience by the animal frame, by 
reason of its perfect uniformity in every direction, and it may 
be doubled, or even tripled without injury. 

A barometer may be constructed with other liquids besides 
mercury; but, as the height of the column must always bear 
an invei'se proportion to the density of the liquid, the length 
of tube required will be often considerable ; in the case of 
water it will exceed 33 feet. It is seldom that any other 
liquid than mercury is employed in the construction of this 
instrument. The Royal Society of London possess a water- 
barometer at their apartments at Somerset House. Its con- 
struction was attended with great difficulties, and it has been found impos- 
sible to keep it in repair. 

It will now be necessary to consider a most important law which connects 
the volume occupied by a gas with the pressure made upon it, and which is 
thus expressed : — 

The volume of a gas is inversely as the pressure ; the density and elastic 
force are directly as the pressure, and inversely as the volume. 
For instance, 100 cubic inches of gas under a pressure of 30 inches of 
mercury would expand to 200 cubic inches were the pressure reduced to 
one-half, and shrink, on the contrary, to 50 cubic inches if the original pres- 
sure were doubled. The change of density must necessarily be in the 
inverse proportion to that of the volume, and the elastic force follows the 
same rule. 

This, which is usually called the law of Mariotte, is easily demonstrable 
by direct experiment. A glass tube, about 7 feet in length, is closed at one end, 
and bent into the form shown in fig. 1C, the open limb of the siphon being 
the longest. It is next attached to a board furnished with a moveable scale 
Df inches, and enough mercury is introduced to till the bend, the level being 
evenly adjusted, and marked upon the board. Mercury is now poured into 
the tube until it is found that the inclosed air has been reduced to one-half 
of its former volume ; and on applying the scale it will be found that the level 




OF THE ATMOSPHERE. 



39 



(yi the mercury in the open part of the tube stands 
very nearly 30 inches above that in the closed portion. 
The pressure of an additional "atmosphere" has con- 
sequently reduced the bulk of the contained air to 
one-half. If the experiment be still continued until 
the volume of air is reduced to a third, it will be found 
that the column measures 60 inches, and so in like 
proportion as far as the experiment is carried. 

The above instrument is better adapted for illustra- 
tion of the principle than for furnishing rigorous proof 
of the law; this has, however, been clone. MM. Arago 
and Dulong published, in the year 1830, an account of 
certain experiments made by them in Paris, in which 
the law in question had been verified to the extent of 
27 atmospheres. 

All gases are alike subject to this law, and all va- 
pours of volatile liquids, when remote from their points 
of liquefaction. 1 It is a matter of the greatest im- 
portance in practical chemistry, since it gives the 
means of making corrections for pressure, or deter- 
mining by calculation the change of volume which a gas 
would suffer by any given change of external pressure. 

Let it be required, for example, to solve the fol- 
lowing problem: — We have 100 cubic inches of gas in 
a graduated jar, the barometer standing at 29 inches; 
how many cubic inches will it occupy when the column 
rises to 30 inches ? — Now the volume must be inversely 
as the pressure ; consequently a change of pressure in 
the proportion of 29 to 30 must be accompanied by 
a change of volume in the proportion of 30 to 29 ; 30 
cubic inches of gas contracting to 29 cubic inches 
under the conditions imagined. Hence the answer : 

30 : 29 = 100 : 96-67 cubic inches. 
The reverse of the operation will be obvious. The 
practical pupil will do well to familiarize himself with 
these simple calculations of correction for pressure. 

From what has been said respecting the easy com- 
pressibility of gases, it will be at once seen that the 
atmosphere cannot have the same density, and cannot 
exert equal pressures at different elevations above the 
sea-level, but that, on the contrary, these must diminish 
with the altitude, and very rapidly. The lower strata 
of air have to bear the weight of those above them ; 
they become, in consequence, deeper and more com- 
pressed than the upper portions. The following table, 
which is taken from Prof. Graham's work, shows in a very simple 
the rule followed in this respect. 

Height above the 
sea, in miles. Yolume of air. 

1 

2-705 2 

5-41 4 



Height of baronietc 
in inches. 

30 

15 



8-115 
10-82 
lS-5'25 
1G-23 



16 



1-875 

0-9375 
0-4CS75 



1 When near the liquefying point the law no longer holds; the volume diminishes viurt 
rapidly than tho theory indicates, a smaller amount of pressure being then sufficient. 



40 PHYSICAL CONSTITUTION OF THE ATMOSPHERE 



|- 



Fig. 17. The numbers in the first column form an arithmetical series, 

by the constant addition of 2-705 ; those in the second column an 
increasing geometrical series, each being the double of its prede- 
cessor; and those in the third, a decreasing geometrical series, 
in which each number is the half of that standing above it. In 
ascending in the air in a balloon, these effects are •well ob- 
served ; the expansion of the gas within the machine, and the 
fall of the mercury in the barometer, soon indicate to the voya- 
ger the fact of his having left below him a considerable part of 
the whole atmosphere. 

The invention of the barometer, which took place in the year 
1643, by Torricelli, a pupil of the celebrated Galileo, speedily 
led to the observation that the atmospheric pressure at the 
same level is not constant, but possesses, on the contrary, a 
small range of variation, seldom exceeding in Europe 2 or 2-5 
inches, and within the tropics usually confined within much 
narrower limits. Two kinds of variations are distinguished ; 
regular or horary, and irregular or accidental. It has been 
observed, that in Europe the height of the barometer is greatest 
at two periods in the twenty-four hours, depending upon the 
season. In winter, the first maximum takes place about 9 a. m., 
the first minimum at 3 p. m., after which the mercury again 
rises and attains its greatest elevation at 9 in the evening ; in 
summer these hours of the aerial tides are somewhat altered. 
The accidental variations are much greater in amount, and 
render it extremely difficult to trace the regular changes above 
mentioned. 

The barometer is applied with great advantage to the mea- 
surement of accessible heights, and it is also in daily use for 
foretelling the state of the weather ; its indications are in this 
respect extremely deceptive, except in the case of sudden and 
violent storms, which are almost always preceded by a rapid 
fall in the mercm*ial column. It is often extremely useful in 
this respect at sea. 

To the practical chemist, a moderately good barometer is an 
- Jr-J jf* indispensable article, since in all experiments in which volumes 
of gases are to be estimated, an account must be taken of the 
pressure of the atmosphere. The marginal drawing represents 
a very convenient and economical siphon barometer for this 
purpose. A piece of new and stout tube, of about one-third of 
an inch in internal diameter, is procured at the glass-house, 
sealed at one extremity, and bent into the siphon form, as repre- 
sented. Pure and warm mercury is next introduced by successive portions 
until the tube is completely filled, and the latter being held in an upright 
position, the level of the metal in the lower and open limb is conveniently 
adjusted by displacing a portion by a stick or glass rod. The barometer is, 
lastly, attached to a board, and furnished with a long scale, made to slide, 
which may be of box-wood, with a slip of ivory at each end. When an ob- 
servation is to be taken, the lower extremity or zero of the scale is placed 
exactly even with the mercury in the short limb, and then the height of the 
column at once read off. 



HEAT. 



41 



HEAT. 

It will be convenient to consider the subject of Heat under several sec- 
tions, and in the following order: — 

1. Expansion of bodies, or effects of variations of temperature in altering 

their dimensions. 

2. Conduction, or transmission of heat. 

3. Change of state. 

4. Capacity of bodies for heat. 

The phenomena of radiation must be deferred until a sketch has been 
given of the science of light. 

EXPANSION. 

If a bar of metal (fig. 18) be taken, of such magnitude as to fit accurately 
to a gauge when cold, heated considerably, and again applied to the guage, it 
will be found to have become enlarged in all its dimensions. "When cold, it 
will once more enter the gsmge. 

Again, if a quantity of liquid contained in a glass bulb (fig. 19), furnished 
with a narrow neck, be plunged into hot water, or exposed to any other 



Fig. 18. 



Fig. 19. 



Fig. 20. 



jap 



n 




source of heat, the liquid will mount in the stem, showing that its volume 
has been increased. 

Or, if a portion of air be confined in any vessel (fig. 20), the application of 
a slight degree of heat will suffice to make it occupy a space sensibly larger. 

This most general of all the effects of heat furnishes in the outset a prin- 
ciple, by the aid of which an instrument can be constructed capable of taking 
cognizance of changes of temperature in a manner equally accurate and con- 
venient: such an instrument is the thermometer. 

A capillary glass tube is chosen, of uniform diameter one extremity is 
closed and expanded into a bulb, by the aid of the blowpipe Same, iand the 
4* 



42 HEAT. 

other somewhat drawn out, and left open. The bulb is now cautiously heated 
by a spirit lamp, and the open extremity plunged into a vessel of mercury, 
a portion of which rises into the bulb when the latter cools, replacing the 
air which had been expanded and driven out by the heat. By again applying 
the flame, and causing this mercury to boil, the remainder of the air is easily 
expelled, and the whole space filled with mercurial vapour, on the condensa- 
tion of which the metal is forced into the instrument by the pressure of the 
air, until it becomes completely filled. The thermometer thus filled is now 
to be heated until so much mercury has been driven out by the expansion 
of the remainder, that its level in the tube shall stand at common tempera- 
tures at the point required. This being satisfactorily adjusted, the heat is 
once more applied, until the column rises quite to the top ; and then the 
extremity of the tube is hermetically sealed by the blowpipe. The retraction 
of the mercury on cooling now leaves an empty space in the upper part of 
the tube, which is essential to the perfection of the instrument. 

The thermometer has yet to be graduated ; and to make its indications 
comparable with those of other instruments, a scale, having certain fixed 
points, at the least two in number, must be adapted to it. 

It has been observed, that the temperature of melting ice, that is to say, 
of a mixture of ice and water, is always constant ; a thermometer, already 
graduated, plunged into such a mixture, always marks the same degree of 
temperature, and a simple tube filled in the manner described, and so treated, 
exhibits the same effect in the unchanged height of the little mercurial 
column, when tried from day to day. The freezing-point of water, or melting- 
point of ice, constitutes then one of the invariable temperatures demanded. 

Another is to be found in the boiling-point of water, which is always the 
same under similar circumstances. A clean metallic vessel is taken, into 
which pure water is put and made to boil ; a thermometer placed in the 
boiling liquid just so deep as is necessary to cover the bulb, invariably marks 
the same degree of temperature so long as the height of the barometer re- 
mains unchanged. 

The tube having been carefully mnrked with a file at these two points, it 
remains to divide the interval into degrees ; this is entirely arbitrary. In 
the greater part of Europe and in America, the scale called centigrade is em- 
ployed; the space in question being divided into 100 parts, the zero being 
placed at the freezing point of watei\ The scale is continued above and 
below these points, numbers below being distinguished by the negative 
sign. 

In England the very inconvenient division of Fahrenheit is still in use ; 
the above space is divided into 180 degrees, but the zero, instead of starting 
from the freezing-point of water, is placed 32 degrees below it, so that the 
temperature of ebullition is expressed by the number 212°. 

The plan of Reaumur is nearly confined to a few places in the north of 
Germany and to Russia ; in this scale the freezing-point of water is made 
0°, and the boiling-point 80°. 

It is unfortunate that an uniform system has not been generally adopted 
in graduating thermometers ; this would render unnecessary the labour which 
now so frequently has to be performed of translating the language of one 
scale into that of another. To effect this, presents, however, no great diffi- 
culty. Let it be required, for example, to know the degree of Fahrenheit'^ 
scale which corresponds to 60° centigrade. 

100° C. = 180° F., or 5° C. = 9° F. 

Consequently, 

5:9 = 00 : 10S. 



HEAT 



43 



But, then, as Fahrenheit's scale commences with 32° instead of 0°, that 
number must be added to the result, making 00° C. = 140° F. 

The rule then will be the following : — To convert centigrade degrees into 
Fahrenheit degrees, multiply by 9, divide the product by 5, and add 32 ; to 
convert, Fahrenheit degrees into centigrade degrees, subtract 32, multiply 
by 5, and divide by 9. 

The reduction of negative degrees, or those below zero of either scale, 
presents rather more apparent difficulty ; a little consideration, however, 
will render the method obvious, the interval between the two zero-points 
being borne in mind. 

Mercury is usually chosen for making thermometers, on account of its 
regularity of expansion within certain limits, and because it is easy to have 
the scale of great extent, from the large interval between the freezing and 
boiling-points of the metal. Other substances are sometimes used; alcohol 
is employed for estimating very low temperatures. 

Air-thermometers are also used for some few particular purposes ; indeed, 
the first thermometer ever made was of this kind. There are two modifica- 
tions of this instrument; in the first, the liquid into which the tube dips is 
open to the air, and in the second (fig. 21), the atmosphere is completely 
excluded. The effects of expansion are in the one case complicated with 
those arising from changes of pressure, and in the other cease to be visible 
at all when the whole instrument is subjected to alterations of temperature, 
because the air in the upper and lower reservoir, being equally affected by 
such changes, no alteration in the height of the fluid column can occur. 
Accordingly, such instruments are called differential thermometers, since 
they serve to measure differences of temperatures between the two portions 
of air, while changes affecting both alike are not indicated. Fig. 22 shows 
another f^rm of the same instrument. 



Fig. 21. 



Tig. 22. 




The air-thermometer may be employed for measuring all temperatures, 
from the lowest to the Jwghest; M. Pouillet has described one by which the 
heat of an air-furnace could be measured. The reservoir of this instrument 
is of platinum, and it is connected with a piece of apparatus by which the 
increase of volume experienced by the included air is determined. 

All bodies are enlarged in their dimensions by the application of heat, 
and reduced by its abstraction, or, in other words, contract on being artifi- 



u 



II EAT. 



cially cooled ; this effect takes place to a comparatively small extent with 
solids, to a larger amount in liquids, and most of all in the case of gases. 

Each solid and liquid has a rate of expansion peculiar to itself; gases, on 
the contrary, all expand alike for the same increase of heat. 

The difference of expansibility among solids is very easily illustrated by 
the following arrangement : a thin straight bar of iron is firmly fixed by 
numerous rivets, to a similar bar of brass ; so long as the temperature at 
which the two metals were united remains unchanged, the compound bar 
preserves its straight figure ; but any alteration of temperature gives rise to 
a corresponding curvature. Brass is more dilatable than iron ; if the bar 
be heated, therefore, the former expands more than the latter, and forces 
the straight bar into a curve, whose convex side is the brass; if it be arti- 
ficially cooled, the brass contracts more than the iron, and the reverse of 
this effect is produced. 

Fig. 23. 




Fig. 24. 



This fact has received a most valuable application. It is no* necessary 
to insist on the importance of possessing instruments for the accurate mea- 
surement of time ; such are absolutely indispensable to the 
successful cultivation of astronomical science, and not less use- 
ful to the navigator, from the assistance they give him in find- 
ing the longitude at sea. For a long time, notwithstanding the 
perfection of finish and adjustment bestowed upon clocks and 
watches, an apparently insurmountable obstacle presented 
itself to their uniform and regular movement ; this obstacle 
was the change of dimensions to which the regulating parts of 
the machine were subject by alterations of temperature. A 
clock may be defined as an instrument for registering the num- 
ber of beats made by a pendulum : now the time of oscillation 
of a pendulum defends pri?icipaUy upon its length ; any altera- 
tion in this condition will seriously affect the rate of the clock. 
The material of which the rod of the pendulum is composed is 
subject to expansion and contraction by changes of tempera- 
ture-; so that a pendulum adjusted to vibrate seconds at 60° 
(15°-5C) would go too slow when the temperature rose to 70° 
(21°-1C), from its elongation, and too fast when the tempera- 
ture fell to 50° (10°C), from the opposite cause. 

This great difficulty has been overcome ; by making the rod 
of a number of bars of iron and brass, or iron and zinc, 
metals whose rates of expansion are different, and arranging 
these bars in such a manner that the expansion in one direction 
of the iron shall be exactly compensated by that in the oppo- 
site direction of the brass or zinc, it is possible to maintain 
under all circumstances of temperature an invariable distance between the 
points of suspension and of oscillation. This is often called the gridiron 



HEAT. 



45 



the shaded 



25. 



Fig. 26. 



pendulum ; fig. 24 will clearly illustrate its principle 
bars are supposed to be iron and the others brass. 

A still simpler compensation pendulum (fig. 25) is thus con- 
structed. The weight or bob, instead of being made of a disc 
of metal, consists of a cylindrical glass jar containing mercury, 
which is held by a stirrup at the extremity of the steel pendulum- 
rod. The same increase of temperature which lengthens this rod, 
causes the volume of the mercury to enlarge, and its level to rise 
in the jar ; the centre of gravity is thus elevated, and by properly 
adjusting the quantity of mercury in the glass, the virtual length 
of the pendulum may be made constant. 

In watches, the governing power is a horizontal weighted 
wheel, set in motion in one direction by the machine itself, and in 
the other by a fine spiral spring. The rate of going depends 
greatly on the diameter of this wheel, and the diameter is of 
necessity subject to variation by change of temperature. To 
remedy the evil thus involved, the circumference of the balance- 
wheel is made of two metals having different rates of expansion, 
fast soldered together, the most expansible being on the outside. 
The compound rim is also cut through in two or more places, as 
represented in fig. 26. When the watch is exposed to a high tempera- 
ture, and the diameter of the wheel becomes enlarged by expansion, each 
segment is made, by the same agency, to assume a 
sharper curve, whereby its centre of gravity is 
thrown inwards, and the expansive effect com- 
pletely compensated. Many other beautiful appli- 
cations of the same principle might be pointed 
out; the metallic thermometer of M. Breguet is 
one of these. 

Mr. Daniell very skilfully applied the expansion 
of a rod of metal to the measurement of tempera- 
tures above those capable of being taken by the 
thermometer. A rod of iron or platinum, about 
five inches long, is dropped into a tube of black- 
lead ware ; a little cylinder of baked porcelain is 
put over it, and secured in its place by a platinum strap and a wedge of 
porcelain. When the whole is exposed to 
heat, the expansion of the bar drives 
forward the cylinder, which moves with a 
certain degree of friction, and shows, by 
the extent of its displacement, the length- 
ening which the bar had undergone. It 
remains, therefore, to measure the amount 
of this displacement, which must be very 
small, even when the heat has been ex- 
ceedingly intense. This is effected by the 
contrivance shown in fig. 27, in which 
the motion of the longer arm of the 
lever Tarrying the vernier of the scale is 
multipled by 10, in consequence of its 
superior length. The scale itself is made 
comparable with that of the ordinary 
thermometer, by plunging the instrument 
into a bath of mercury near its point of 
congelation, and afterwards into another of the same metal in a boiling 
state, and marking off the interval. By this instrument the melting-point 





46 HEAT. 

of cast iron was fixed at 2786° Fahrenheit (1530°C), and the greatest heat 
of a good wind-furnace at about 3300° (1815°C). 

The actual amount of expansion which different solids undergo by the 
same increase of heat, has been carefully investigated. The following are 
some of the results obtained by MM. Lavoisier and Laplace. The fraction 
indicates the amount of expansion in length suffered by rods of the under- 
rentioned bodies in passing from 32° (0°C) to 212° (100°C). 



English flint glass 
Common French glass 
Glass without lead 
Another specimen 
Steel untempered 
Tempered steel . ^j 



i 

__1 

114 1 

1 

1142 

1 

10 90 
_1_ 

or" 



Soft iron . . . ,f T 

Gold . . . ^ 

Brass . . . ^ 

Silver .... ^ ¥ 

Lead . . . | r 



Copper 



From the linear expansion, the cubic expansion (or increase of volume) 
may be easily calculated. When an approximation only is wanted, it will be 
sufficient to triple the fraction expressing the increase in one dimension. 

Metals appear to expand pretty uniformly for equal increments of heat 
within the limits stated, but above the boiling-point of water the rate of 
expansion becomes irregular and more rapid. 

The force exerted in the act of expansion is very great ; in laying down 
railways, building iron bridges, erecting long ranges of steam-pipes, and in 
executing all works of the kind in which metal is largely used, it is indis- 
pensable to make provision for these changes of dimensions. 

A very useful little application of expansion by heat is that to the cutting 
of glass by a hot iron ; this is constantly practised in the laboratory for a 
great variety of purposes. The glass to be cut is marked "with ink in the 
wished-for direction, and then a crack commenced by any convenient method, 
at some distance from the desired line of fracture, may be led by the point 
of a heated iron rod along the latter with the greatest precision. 

Expansion of Fluids. — The dilatation of a fluid may be determined by fill- 
ing with it a thermometer, in which the relation between the capacity of the 
ball and that of the stem is exactly known, and observing the height of the 
column at different temperatures. It is necessary in this experiment to take 
into account the effects of the expansion of the glass itself, the observed re- 
sult being evidently the difference of the two. 

Liquids vary exceedingly in this particular. The following table is taken 
from Peclet's Elemens de Physique. 

Apparent Dilatation in Glass between 32° (0°C) and 212° (100°C). 

Water 21 

Hydrochloric acid, sp. gr. 1*137 . . . •2V 

Nitric acid, sp. gr. 1*4 -g- 

Sulphuric acid, sp. gr. T85 yy 

Ether T V 

Olive oil Y2 

Alcohol 7 

Mercury V? 

Most of these numbers must be taken as representing mean results. For 
there are few fluids which, like mercury, expand regularly between these 
temperatures. Even mercury above 212° (100 o C) expands irregularly, as 
the following table shows. 



II EAT 



4? 



Absolute Expansion of Mercury for 180°. 

Between 32° (0°C) and 212° (100°C) .... 7 U 

Between 212° (100°C) and 392° (200°C) .... j^ 3 

Between 392° (200°C) and 572° (300°G) .... ^'. 

The absolute amount of expansion of mercury is, for many reasons, a 
point of great importance ; it has been very carefully determined by a me- 
thod independent of the expansion of the containing vessel. The apparatus 
employed for this purpose by MM. Dulong and Petit is shown in fig. 28, di- 
vested, however, of many of its subordinate parts. It consists of two up- 
right glass tubes, connected at their bases by a horizontal tube of much 
smaller dimensions. Since a free communication exists between the two 
tubes, mercury poured into the one will rise to the same level in the other, 
provided its tempei*ature is the same in both tubes ; when this is not the 
case, the hottest column will be the tallest, because the expansion of the 
metal diminishes its specific-gravity, and the law of hydrostatic equilibrium 
requires that the heights of such columns should be inversely as their den- 
sities. By the aid of the outer cylinders, one of the tubes is maintained 
constantly at 32° (0°C), while the other is raised, by means of heated water 
or oil, to any required temperature. The perpendicular heights of the 
columns may then be read off by a horizontal micrometer telescope, moving 
on a vertical divided scale. 



Fig. 28 




These heights represent volumes of equal weight, because volumes of 
equal weight bear an inverse proportion to the densities of the liquids, so 
that the amount of expansion admits of being very easily calculated. Thus, 
let the column at 32° (0°C) be 6 inches high, and that at 212° (100°C) 6-108 
inches, the increase of height, 108 on G,000, or -^.-^ part of the whole, must 
represent the absolute cubical expansion. 

The indications of the mercurial thermometer are inaccurate when very 
high ranges of temperature are concerned, from the increased expansibility 
of the metal ; on this account, a certain correction is necessary in many ex- 
pei-iments, and tables for this purpose have been drawn up. 1 

An exception to the regularity of expansion in fluids, exists in the case 
of water; it is so remarkable, and its consequences so important, that it is 
necessary to advert to it particularly. 

Let a large thermometer-tube be filled with water at the common tempe- 

1 Below 400° Fahrenheit (204°-4C!) the error may be neglected; at 500° (260°C) it v about 
"»°; at 030° (332°-5C) 6°.— Regnamifc 



48 HEAT. 

rature of the air, and then artificially cooled. The liquid will be observed 
to contract regularly, until the temperature falls to about 40° (4°-4C), or 8° 
above the freezing-point. After this, a farther reduction of temperature 
causes expansion instead of contraction in the volume of the water, and this 
expansion continues until the liquid arrives at its point of congelation, when 
so sudden and violent an enlargement takes place, that the vessel is almost 
invariably broken. At the temperature of 40° (4°-4C), or more correctly, 
perhaps, 39° -5 (4°'1C), water is at its maximum density; increase or dimi- 
nution of heat produces upon it, for a short time, the same effect. 

A beautiful experiment of Dr. Hope illustrates the same fact. If a tall 
jar filled with water at 50° (10°C) or 60° (15°-5C) and having in it two 
small thermometers, one at the bottom and the other near the surface, be 
placed at rest in a very cold room, the following changes will be observed. 
The thermometer at the bottom will fall more rapidly than that at the top, 
until it has attained the temperature of 40° (4°-4C) after which it will re- 
main stationary. At length the upper thermometer will also mark 40° 
(4°-4C) but still continue to sink as rapidly as before, while that at the bot- 
tom remains stationary. It is easy to explain these effects : the water in 
the upper part of the jar is rapidly cooled by contact with the air ; it be- 
comes denser in consequence, and falls to the bottom, its place being sup- 
plied by the lighter and warmer liquid, which in its turn suffers the same 
change ; and this circulation goes on until the whole mass of water has ac- 
quired its condition of maximum density, that is, until the temperature has 
fallen to 40° (4°-4C). Beyond this, loss of heat occasions expansion instead 
of contraction, so that the very cold water on the surface has no tendency 
to sink, but rather the reverse. 

This singular anomaly in the behaviour of water is attended by the most 
beneficial consequences, in shielding the inhabitants of the waters from ex- 
cessive cold. The deep lakes of the North American Continent never freeze, 
the intense and prolonged cold of the winters of those regions being insuffi- 
cient to reduce the temperature of such masses of water to 40° (4°*4C). 
Ice, however, of great thickness forms over the shallow portions, and the 
rivers, and accumulates in mounds upon the beaches, where the waves are 
driven up by the winds. 

Sea-water has a maximum density at the same temperature as fresh 
water. The depths of the Polar Seas exhibit this temperature throughout 
the year, while the surface-water is in summer much above, and in winter 
much below, 40° (4°-4C) ; in both cases being specifically lighter than water 
at that temperature. This gradual expansion of water cooled below 40° 
(4°-4C) must be carefully distinguished from the great and sudden increase 
of volume it exhibits in the act of freezing, and in which respect it resem- 
bles many other bodies which expand on solidifying. It may be observed 
that the force thus exerted by freezing water is enormous. Thick iron shells 
quite filled with water, and exposed with their fuse-holes securely plunged, 
to the cold of a Canadian winter night, have been found the following morn- 
ing split in fragments. The freezing of water in the joints and crevices of 
rocks is a most potent agent in their disintegration. 

Expansion of Gases. — This is a point of great practical importance to the 
chemist, and happily we have very excellent evidence upon the subject. The 
following four propositions exhibit, at a single view, the principal facts of 
the case : — 

1. All gases expand alike for equal increments of heat; and all vapours, 

when remote from their condensing-points, follow the same law. 

2. The rate of expansion is not altered by a change in the state of com • 

pression, or clastic force of the gas itself. 



HEAT. 49 

8. The rate of expansion is uniform for all degrees of heat. 
4. The actual amount of expansion is equal to ^^ part of the volume of 
the gas at 0° Fahrenheit, for each degree of the same scale. 1 

It -will be unnecessary to enter into any description of the methods of in- 
vestigation by which these results have been obtained ; the advanced student 
will find in Pouillet's Elemens de Physique, and in the papers of MM. Magnus a 
and Regnault 3 all the information he may require. 

Tn the practical manipulation of gases, it very often becomes necessary to 
make a correction for temperature, or to discover how much the volume of 
a gas would be increased or diminished by a particular change of tempera- 
ture ; this can be effected with great facility. Let it be required, for ex- 
ample, to find the volume which 100 cubic inches of any gas at 50° (10°C) 
would become on the temperature rising to 60° (15° -5C). 

The rate of expansion is ¥ |- ¥ of the volume at 0° for each degree ; or 460 
measures at 0° become 461 at 1°, 462 at 2°, •• 460 -J- 50 = 510 at 50°, and 
460 -f 60 = 520 at 60°. Hence 

Meas. at 50°. Meas. at 60°. Meas. at 50°. Meas. at 60°. 

510 : 520 = 100 : 101-96. 

If this calculation is required to be made on the centigrade scale, it must 
be remembered that the zero of that scale is the melting point of ice. Above 
this temperature the expansion for each degree of the centigrade scale is 
-_i f _ of the original volume. 

This, and the correction for pressure, are operations of very frequent oc- 
currence in chemical investigations, and the student will do well to become 
familiar with them. 



Note. — Of the four propositions stated in the text, the first and second 
have quite recently been shown to be true within certain limits only ; and 
the third, although in the highest degree probable, would be very difficult to 
demonstrate rigidly ; in fact, the equal rate of expansion of air is assumed 
in all experiments on other substances, and becomes the standard by which 
the results are measured. 

The rate of expansion for the different gases is not absolutely the same, 
but the difference is so small, that for most purposes it may with perfect 
safety be neglected. Neither is the state of elasticity altogether indifferent, 
the expansion being sensibly greater for an equal rise of temperature when 
the gas is in a compressed state. 

It is important to notice, that the greatest deviations from the rule are exhi- 
bited by those gases which, as will hereafter be seen, are most easily lique- 
fied, such as carbonic acid, cyanogen, and sulphurous acid, and that the dis- 
crepancies become smaller and smaller as the elastic force is lessened ; so 
that, if means existed for comparing the different gases in states equally dis- 
tant from their points of condensation, there is reason to believe that the 
la^ would be strictly fulfilled. 

The experiments of MM. Dulong and Petit give for the rate of expansion 
■£-}■$ of the volume at 0° : this is no doubt too high. Those of Rudburg give 
5-| T ; of Magnus T ^ ; and of Regnault T ^ : the fraction T -g— is adopted in 
the test as a convenient number, sufficiently near the mean of the three pre- 
ceding, to answer all purposes. 

1 Ov the amount of expansion is equal to l-492d part of the volume the gas occupies at 
32°F. for each decree of Fahrenheit's scale. On the centigrade scale the expansion is 
l-273d part of the bulk at 0OC — R. B. 

9 Poggendorffs Annalen, ir. 1. 8 Ann. Chim. et Phys., 3rd series, iv 5. and v. 52. 

5 



50 



HEAT. 



Pig. 29. 



Ztl 




The ready expansibility of air by heat gives rise to the phenomena of 
winds. In the temperate regions of the earth these are very variable and 
uncertain, but within and near the tropics a much greater regularity pre- 
vails ; of this the trade-winds furnish a beautiful example. 

The smaller degree of obliquity with which the sun's rays fall in the 
localities mentioned, occasions the broad belt thus stretching round the earth 
to become more heated than any other part of the surface. The heat thus 
acquired by absorption is imparted to the low- 
est stratum of air, which, becoming expanded, 
rises, and gives place to another, and in this 
manner an ascending current is established, — 
the colder and heavier air streaming in late- 
rally from the more temperate regions, north 
and south, to supply the partial vacuum thus 
occasioned. A circulation so commenced will 
be completed in obedience to the laws of hydro- 
statics, by the establishment of counter-cur- 
rents in the higher parts of the atmosphere, 
having directions the reverse of those on the 
surface. (Fig. 29.) 

Such is the effect produced by the unequal 
heating of the equatorial parts, or, more correctly, such would be the effect 
were it not greatly modified by the earth's movement of rotation. 

As the circumference of the earth is, in round numbers, about 24,000 
miles, and since it rotates on its axis, from west to east, once in 24 hours, 
the equatorial parts must have a motion of 1000 miles per hour; this velo- 
city diminishes rapidly towards each pole, where it is reduced to nothing. 

The earth in its rotation carries with it the atmosphere, whose velocity 
of movement corresponds, in the absence of disturbing causes, with that 
part of the surface immediately below it. The 
air which rushes towards the equator, to sup- 
ply the place of that raised aloft by its dimin- 
ished density, brings with it the degree of mo- 
mentum belonging to that portion of the 
earth's surface from which it set out, and as 
this momentum is less than that of the earth, 
under its new position, the earth itself travels 
faster than the air immediately over it, thus 
producing the effect of a wind blowing in a 
contrary direction to that of its own motion. 
The original north and south winds are thus 
deviated from their primitive directions, and 
made to blow more or less from the eastward, 
so that the combined effects of the unequal 
heating and of the movement of rotation is to generate in the northern hemi- 
sphere a constant north-east wind, and in the southern hemisphere an equally 
constant south-east wind. (Fig. 30.) 

In the same manner the upper or return current is subject to a change of 
direction in the reverse order; the rapidly-moving wind of the tropics, trans- 
ferred laterally towards the poles, is soon found to travel faster than the 
earth beneath it, producing the effect of a westerly wind, which modifies the 
primary current. 

The 'regularity of the trade-winds is much interfered with by the neigh- 
bourhood^ large continents, which produce local effects upon a scale suf- 
ficiently great to modify deeply the direction and force of the wind. This 
is the case in the Indian Ocean. They usually extend from about the 2Sth 




HEAT. 51 

degree of latitude in both hemispheres, to within 8° of the equator, hut are 
subject to some variations in this respect. Between them, and also beyond 
their boundaries, lie belts of calms and light variable winds, and beyond 
these latter, extending into higher latitudes in both hemispheres, westerly 
winds usually prevail. The general direction of the trade- wind of the North- 
ern hemisphere is E.N.E., and that of the Southern hemisphere E.S.E. 

The trade-winds, it may be remarked, furnish an admirable physical proof 
of the reality of the earth's movement of rotation. 

The theory of the action of chimneys, and of natural and artificial ven- 
tilation, belongs to the same subject. 

Let the reader turn to the demonstration given of the Archimedean hydro- 
static theorem ; let him once more imagine a body immersed in water, and 
having a density equal to that of the water ; it will remain in equilibrium in 
any part beneath the surface, and for these reasons: — The force which 
presses it downwards is the weight of the body added to the weight of _ the 
column of water above it ; the force which presses it upwards is the weight 
of a column of water equal to the height of both conjoined ; — the density of 
the body is that of water, that is, it weighs as much as an equal bulk of that 
liquid ; consequently, the downward and upward forces are equally balanced, 
and the body remains at rest. 

Next, let the circumstances be altered ; let the Fio . 31# 

body be lighter than an equal bulk of water ; the 
pressure upwards of the column of water, a c, fig. 31, 
is no longer compensated by the downward pressure 
of the corresponding column of solid and water 
above it; the former force preponderates, and the 
body is driven upwards. If, on the contrary, the 
body be specifically heavier than the water, then 
the latter force has the ascendancy, and the body 
ginks. 

All things so described exist in a common chim- 
ney; the solid body, of the same density as that 
of the fluid in which it floats, is represented by 
the air in the chimney-funnel ; the space a b repre- 
sents the whole atmosphere above it. When the air inside and outside the 
chimney is at the same temperature, equilibrium takes place, because the 
downward tendency of the air within is counteracted by the upward pressure 
of that without. 

Now, let the chimney be heated ; the air suffers expansion, and a portion 
is expelled; the chimney therefore contains a smaller weight of air than it 
did before ; the external and internal columns no longer balance each other, 
and the warmer and lighter air is forced upwards from below, and its place 
supplied by cold air. If the brick-work, or other material of which the 
chimney is constructed, retain its temperature, this second portion of air is 
disposed of like the first, and the ascending current continues, so long as 
the sides of the chimney are hotter than the surrounding air. 

Sometimes, owing to sudden changes of temperature in the atmosphere, 
the chimney may happen to be colder than the air about it. The column 
within forthwith suffers contraction of volume ; the deficiency is filled up 
from without, and the column becomes heavier than one of similar height on 
the outside ; the result is, that it falls out of the chimney, just as the heavy 
body sinks in the water, and has its place occupied by air from above. A 
descending current is thus produced, which may be often noticed in summer 
time by the smoke from neighbouring chimneys finding its way imo rooms 
which have been, for a considerable period, without fire. 

The ventilation of mines has long been conducted upon the same principle 



I 
















-b 




111 
111 















000 


Tin 


. 304 


973 


Lead . 


179 


898 


Marble . 


. 23-6 


374 


Porcelain . 


12-2 


363 


Fire-clay 


. 11-4 



52 HEAT. 

and more recently it has been applied to dwelling-houses and assembly- 
rooms. The mine is furnished -with two shafts, or with one shaft, divided 
throughout by a diaphragm of boards; and these are so arranged, that air 
forced down the one shall traverse the whole extent of the workings before 
it escapes by the other. A fire kept up in one of these shafts, by rarefying 
the air within, and causing an ascending current, occasions fresh air to tra- 
verse every part of the mine, and sweep before it the noxious gases, but tot 
frequently present. 

CONDUCTION OF HEAT. 

Different bodies possess very different conducting powers with respect t<s 
heat: if two similar rods, the one of iron and the other of glass, be held in 
the flame of a spirit-lamp, the iron will soon become too hot to be touched, 
while the glass may be grasped with impunity within an inch of the red-hot 
portion. 

Experiments made by analogous, but more accurate methods, have estab- 
lished a numerical comparison of the conducting powers of many bodies ; 
the following may be taken as a specimen : — 

Gold 
Silver . 
Copper . 
Iron 
Zinc 

As a class, the metals are by very far the best conductors, although much 
difference exists between them ; stones, dense woods, and charcoal, follow 
next in order ; then liquids in general, and gases, whose conducting power 
is almost inappreciable. 

Under favourable circumstances, nevertheless, both liquids and gases may 
become rapidly heated ; heat applied to the bottom of the containing vessel 
is very speedily communicated to its contents ; this, however, is not so much 
by conduction as by convection, or carrying. A complete circulation is set 
up ; the portions in contact with the bottom of the vessel get heated, become 
lighter, and rise to the surface, and in this way the heat becomes communi- 
cated to the whole. If these movements be prevented by dividing the vessel 
into a great number of compartments, the really low conducting power of 
the substance is made evident, and this is the reason why certain organic 
fabrics, as wool, silk, feathers, and porous bodies in general, the cavities of 
which are full of air, exhibit such feeble powers of conduction. 

The circulation of heated water through pipes is now extensively applied 
to the warming of buildings and conservatories, and in chemical works a 
serpentine metal tube containing hot oil is often used for heating stills and 
evaporating pans ; the two extremities of the tube are connected with the 
ends of another spiral built into a small furnace at a lower level, and an 
unintermitting circulation of the liquid takes place as long as heat is 
applied. 

CHANGE OF STATE. 

If equal weights of water at 32° (0°C) and water at 174° (78°-8C) be 
mixed, the temperature of the mixture will be the mean of the two temper- 
atures, or 103° (39°-4C). If the same experiment he repeated with snow, 
or finely powdered ice, at 32° (0°C) and water at 174° (78° 8C), the tem- 
perature of the whole will be still only 32° (0°C), but the ici will leave been 
'nelttd 



II E A T . 53 

1 lb. of water at 32° (0°C) ) „ - , . in „ ,ono 4n\ 
1 lb. of water at 174° (78-8C) }= 2 lb " Water at 103 ( o9 °" 4C > 
1 lb. of ice at 32° (0°C) \ = o lb> water at 32 o (0 o C) 

1 lb. of water at l<i° (<8°-8C) J v J 

In the last experiment, therefore, as much heat has been apparently lost 
as would have raised a quantity of water equal to that of the ice through a 
range of 142° (78°-8C). 

The heat, thus become insensible to the thermometer in effecting the lique- 
faction of the ice, is called latent heat, or, better, head of fluidity. 

Again, let a perfectly uniform source of heat be imagined, of such inten- 
sity that a pound of water placed over it would have its temperature raised 
10° (5°-5C) per minute. Starting with water at 32° (0°C), in rather more 
than 14 minutes its temperature would have risen 142° (78°-8) ; but the 
same quantity of ice at 32° (0°C), exposed for the same interval of time, 
would not have its temperature raised a single degree. But, then, it would 
have become water ; the heat received would have been exclusively employed 
in effecting the change of state. 

This heat is not lost, for when the water freezes it is again evolved. If a 
tall jar of water, covered to exclude dust, be placed in a situation where it 
shall be quite undisturbed, and at the same time exposed to great cold, the 
temperature of the water may be reduced 10° or more below its freezing- 
point without the formation of ice ; but then, if a little agitation be com- 
municated to the jar, or a grain of sand dropped into the water, a portion 
instantly solidifies, and the temperature of the whole rises to 32° (0°C) ; 
the heat disengaged by the freezing of a small portion of the water will have 
been sufficient to raise the whole contents of the jar 10° (5°-5C). 

This curious condition of instable equilibrium shown by the very cold 
water in the preceding experiment, may be reproduced with a variety of 
solutions which tend to crystallize or solidify, but in which that change is 
for a while suspended. Thus, a solution of crystallized sulphate of soda in 
its own weight of warm water, left to cool in an open vessel, deposits a large 
quantity of the salt in crystals. If the warm solution, however, be filtered 
into a clean flask, which when full is securely corked and set aside to cool 
undisturbed, no crystals will be deposited, even after many days, until the 
cork is withdrawn and the contents of the flask violently shaken. Crystal- 
lization then rapidly takes place in a very beautiful manner, and the whole 
becomes perceptibly warm. 

The law thus illustrated in the case of water is perfectly general. "When- 
ever a solid becomes a liquid, a certain fixed and definite amount of heat 
disappears, or becomes latent ; and conversely, whenever a liquid becomes 
a solid, heat to a corresponding extent is given out. The amount of latent, 
heat varies much with different substances, as will be seen by the table : — 

.493° (273°-8C) 

. 500 (277 -7C) 

. 550 (305 -5C) 

"When a solid substance can be made to liquefy by a weak chemical attrac- 
tion, cold results, from sensible heat becoming latent. ' This is the principle 
of the many frigorific mixtures to be found described in some of the older 
chemical treatises. When snow or powdered ice is mixed with common salt, 
and a thermometer is plunged into the mass, the mercury sinks to C 
( — 17°-7C), while the whole, after a short period, becomes fluid by the 
attraction between the water and the salt ; such a mixture is very often used 

1 MM. De la Proyostave and Reimault, Ann. Chim. et Pbys., 3d Ferieo, viii. I. 
5* 



Water l 


. 142° (78°-8C) 


Zinc . 


Sulphur . 


. 145 (80 -5C) 


Tin 


Lead . 


. 162 (90 -5C) 


Bismuth 



54 heat. 

in chemical experiments to cool receivers and condense the vapours of vola- 
tile liquids. Powdered crystallized chloride of calcium and snow produce 
cold enough to freeze mercury. Even powdered nitrate of potassa, or sal- 
ammoniac, dissolved in water, occasions a very notable depression of tem- 
perature ; in every case, in short, in which solution is unaccompanied by 
energetic chemical action, cold is produced. 

No relation is to be traced between the actual melting-point of a sub- 
stance, and its latent heat when in a fused state. 

A law of exactly the same kind as that described affects universally the 
gaseous condition ; change of state from solid or liquid to gas is accompa- 
nied by absorption of sensible heat, and the reverse by its disengagement. 
The latent heat of steam and other vapours may be ascertained by a similar 
mode of investigation to that employd in the case of water. 

AVhen water at 32° (0°C) is mixed with an equal weight of water at 212° 
(100°C), the whole is found to possess the mean of the two temperatures, or 
122° (50°C) ; on the other hand, 1 part by weight of steam at 212° (100°C) 
when condensed into cold water, is found to be capable of raising 5-6 parts 
of the latter from the freezing to the boiling-point, or through a range of 
180° (100°C). Now 180 X 5-6 = 1008; that is to say, steam at 212° 
(100°C) in becoming water at 212°, parts with enough heat to raise a weight 
of water equal to its own (if it were possible) 1008° (560°C) of the ther- 
mometer. When water passes into steam, the same quantity of sensible 
heat becomes latent. 

The vapours of other liquids seem to have less latent heat than that of 
water ; the following table is by Dr. Ure, and serves well to illustrate this 
point : — 

Vapour of water 967° (537°-2C) 

alcohol 442 (246 -6C) 

ether 302 (167 -7C) 

" petroleum 178 (98 -8C) 

" oil of turpentine 178 (98 -8C) 

nitric acid 532 (295 -5C) 

" liquor aininonire 837 (145 -0C) 

" vinegar 875 (486 -1C) 

Ebullition is occasioned by the formation of bubbles of vapour within the 
body of the evaporating liquid, which rise to the surface like bubbles of 
permanent gas. This occurs in different liquids at very different tempera- 
tures ; under the same circumstances, the boiling-point is quite constant, 
and often becomes a physical character of great importance in distinguishing 
liquids which much resemble each other. A few cases may be cited in 
illustration : — 

Substance. Boiling-point. 

Ether 96° (35°-5C) 

Bisulphide of carbon 115 (46 -1C) 

Alcohol 177 (80 -5C) 

Water 212 (100 C) 

Nitric acid, strong 248 (120 C) 

Oil of turpentine 312 (155 -5C) 

Sulphuric acid 620 (326 -2C) 

Mercury 662 (350 C) 

For ebullition to take place, it is necessary that the elasticity of the vapour 
should be able to overcome the cohesion of the liquid and the pressure upon 
its surface ; hence the extent to which the boiling-point may be modified. 

Water, under the usual pressure of the atmosphere, boils at 212° (100°C) ; 




II EAT. 55 

in a partially exhausted receiver or on a mountain-top it boils at a much 
lower temperature ; and in the best vacuum of an excellent air-pump, over 
oil of vitriol, which absorbs the vapour, it will often enter into violent 
ebullition while ice is in the act of forming upon the surface. 

On the other hand, water confined in a very strong metallic vessel may -be 
restrained from boiling by the pressure of its own vapour to an almost un- 
limited extent; a temperature of 350° (177°C) or 400° (204°C) is very easily 
obtained ; and, in fact, it is said that it may be made red-hot, and yet retain 
its fluidity. 

There is a very simple and beautiful experiment illustra- 
tive of the effect of diminished pressure in depressing the Kg. 32. 
boiling point of a liquid. A little water is made to boil for 
a few minutes in a flask or retort (fig. 32) placed over a lamp, 
until the air has been chased out, and the steam issues freely 
from the neck. A tightly fitting cork is then inserted, and 
the lamp at the same moment withdrawn. When the 
ebullition ceases it may be renewed at pleasure for a con- 
siderable time by the affusion of cold water, which, by con- 
densing the vapour within, occasions a partial vacuum. 

The nature of the vessel, or rather, the state of its sur- 
face, exercises an influence upon the boiling-point, and this 
to a much greater extent than was formerly supposed. It 
has long been noticed that in a metallic vessel water boils, under the same 
circumstances of pressure, at a temperature one or two degrees below that 
at which ebullition takes place in glass ; but it has lately been shown l that 
by particular management a much greater difference can be observed. If 
two similar glass flasks be taken, the one coated in the inside with a film of 
shellac, and the other completely cleansed by hot sulphuric acid, water 
heated over a lamp in the first will boil at 211° (99°-4C), while in the second 
it will often rise to 221° (105°C) or even higher ; a momentary burst of 
vapour then ensues, and the thermometer sinks a few degrees, after which 
it rises again. In this state the introduction of a few metallic filings, or 
angular fragments of any kind, occasions a lively disengagement of vapour, 
while the temperature sinks to 212° (100°C), and there remains stationary. 
These remarkable effects must be attributed to an attraction between the 
surface of the vessel and the liquid. 2 

1 Marcet, Ann. Chim. et Phys., 3d series, v. 449. 

3 A remarkable modification of the relation between the temperature of liquids and the 
vessel containing them, results where the repulsive action predominates. When a small 
quantity of water is thrown into a red-hot platinum crucible, it assumes a spheroidal form, 
presents no appearance of ebullition, but only a rotary motion, and evaporates very slowly; 
but when the temperature falls to 300°, this spheroidal condition is lost, the liquid boils and 
is soon dissipated. In the spheroidal state there is no contact between the water and metal, 
in consequence of the high tension of the small quantity of vapour which is formed and 
surrounds the globule, but on the fall in temperature, the tension lessens and with it the 
repulsive action, contact takes place and the heat is rapidly communicated to the liquid, 
which at once is converted into steam. So slight is the iuliuence of the caloric of the vessel 
on the contained liquid in this condition, that if liquid sulphurous acid be poured on the 
globule, the water is by the sudden evaporation of the acid converted into ice at the bottom 
of the red-hot crucible. "When a liquid which boils at a low temperature, is thrown on an- 
other heated nearly to ebullition and whose boiling-point is high, the spheroidal state is 
likewise assumed, as water on oil, spirits of turpentine, sulphuric acid, &c, and ether ou 
water, &c. 

As connected with this phenomenon, it has been observed that perfect immunity from the 
caloric of highly heated liquids may be obtained by previously moistening the part to which 
the application is made with some fluid which evaporates at a low temperature. Thus the 
hand, while moistened with ether, may be plunged into boiling-water without even the sen- 
sation of heat. When wet with water "it may be dipped into melted lead without injury or 
strong sensation of heat, and still less is perceived if alcohol or ether be used. A similar 
experiment k;>s been performed with melted cast-iron as it runs from the furnace, and tho 



56 



HEAT, 



A cubic inch of water in becoming steam under the ordinary pressure of 
the atmosphere expands into 1696 cubic inches, or nearly a cubic foot. 

Steam, not in contact with water, is affected by heat in precisely the same 
manner as the permanent gases ; its rate of expansion and increase of elastic 
force are the same. When water is present, however, this is no longer the 
case, but on the contrary, the elastic force increases in a far more rapid 
proportion. 

This elastic force of steam in contact with water, at different temperatures, 
has been very carefully determined by MM. Arago and Dulong, and very 
lately by M. Regnault. The force is expressed in atmospheres ; the abso- 
lute pressure upon any given surface can be easily calculated, allowing 
14-6 lb. to each atmosphere. The experiments were carried to twenty-five 
atmospheres, at which point the difficulties and danger became so great as 
to put a stop to the inquiry; the rest of the table is the result of calcula- 
tions founded on the data so obtained. 



Pressure of steam 


Corresponding 


Pressure of steam 


Corresponding 


in atmospheres. 


temperatxire. 


in atmospheres. 


temperature. 




P. 


c. 




P. 


c. 


1 


.... 212° 


100° 
112 -2 


13 

14 


... 381° 
... 387 


194° 


1-5 


.... 234 


197 -7 


2 


.... 251 


121 -2 


15 


... 393 


200 -5 


2-5 


.... 2G4 


128 -8 


16 


... 398 


203 -1 


3 


.... 275 


135 
140 -5 


17 

18 


... 404 
... 409 


206 -2 


3-5 


.... 285 


209 -4 


4 


.... 294 


145 -5 


19 


... 414 


212 -2 


4-5 


.... 300 


148 -8 


20 


... 418 


214 -4 


5 


.... 308 


153 -1 


21 


... 423 


217 -2 


5-5 


.... 314 


156 -2 


22 


... 427 


219 -4 


6 


.... 320 


160 


23 


... 431 


221 -2 


6-5 


.... 326 


163 -1 


24 


... 436 


224 -4 




332 


166 -2 
169 -4 


25 

30 


... 439 
... 457 


226 -1 


7-5 


.... 337 


236 -1 


8 


.... 342 


172 -2 


35 


... 473 


245 -1 


9 


.... 351 


177 -2 
181 -2 


40 

45 


... 487 
... 491 


252 -7 


10 


359 


255 


11 


. .. 367 


186 -1 
190 


50 


... 511 


266 -1 


12 


.... 374 





It is a very remarhable fact, that the latent heat of steam diminishes as 
the temperature of the steam rises, so that equal weights of steam thrown 
into cold water exhibit nearly the same heating power, although the actual 
temperature of the one portion may be 212° (100°C), and that of the other 
250° (176°-2C) or 400° (204°-4C). This also appears true with temperatures 
below the boiling-point; so that it seems, to evaporate a given quantity of 
water the same absolute amount of heat is required, whether it be performed 
slowly at the temperature of the air, in a manner presently to be noticed, or 
whether it be boiled off under the pressure of twenty atmospheres. It is 
for this reason that the process of distillation in vacuo at a temperature 
which the hand can bear, so advantageous in other respects, can effect no 
direct saving in fuel. 1 



rtrv parts subjected to the radiant caloric have teen found more affected than that exposed 
to the molted metal. 

The immunity in the case of using water as the moistening a<rcnt arises from the fact that 
the temperature of the globule in the spheroidal state is much below the boiling-point of the 
liquid. — R. B. 

■ The proposition in the text, of the sum of the latent and sensible heats of steam being a 
constant quantity, is known by the name of Wait's law, having been deduced by that illus- 



H EAT. 



57 



Fis. 33. 




Fig. 34. 



The economical applications of steam are numerous and extremely valu- 
able; they may be divided into two classes: those in which the heating 
power is employed, and those in which its elastic force is brought into use. 

The value of steam as a source of heat depends 
upon the facility with which it may be conveyed to 
distant points, and upon the large amount of latent 
heat it contains, which is disengaged in the act of 
condensation. An invariable temperature of 212° 
(100°C), or higher, may be kept up in the pipes or 
other vessels in which the steam is contained by 
the expenditure of a very small quantity of the 
latter. Steam-baths of various forms are used in 
the arts with great convenience, and also by the 
scientific chemist for drying filters and other ob- 
jects where excessive heat would be hurtful; a 
very good instrument of the kind was contrived 
by Mr. Everitt. It is merely a small kettle (fig. 
33), surmounted by a double box or jacket, into 

which the substance to be dried is put, and loosely covered by a card. The 
apparatus is placed over a lamp, and may be left without attention for many 
hours. A little hole in the side of the jacket 
gives vent to the excess of steam. 

The principle of the steam-engine may 
be described in a few words ; its mechanical 
details do not belong to the design of the 
present volume. The machine consists es- 
sentially of a cylinder of metal, a (fig. 34), 
in which works a closely-fitting solid piston, 
the rod of which passes, air-tight, through 
a stuffing-box at the top of the cylinder, 
and is connected with the machinery to be 
put in motion, directly, or by the interven- 
tion of an oscillating beam. A pipe commu- 
nicates with the interior of the cylinder, and 
also with a vessel surrounded with cold 
water, called the condenser, marked b in the 
sketch, and into which a jet of cold water 
can at pleasure be introduced. A sliding- 
valve arrangement, shown at c, serves to 
open a communication between the boiler 
and the cylinder, and the cylinder and the 
condenser, in such a manner that while the 
steam is allowed to press with all its force 
upon one side of the piston, the other, open 
to the condenser, is necessarily vacuous. 
The valve is shifted by the engine itself at 
the proper moment, so that the piston is al- 
ternately driven by the steam up and down 
against a vacuum. A large air-pump, not 
shown in the engraving, is connected with the 
condenser, and serves to remove any air that may enter the cylinder, and 
also the" water produced by condensation, together with that which may have 
been injected. 

Such is the vacuum ov condensing steam-engine. In what is called the 




trious man from experiments of his own. It has always agreed well with the rough practical 
results obtained by engineers, and has lately been confirmed to a great extent, aJUiougb. not 
completely, by a series of elaborate experiments by M. Kegnault. 



58 



nE AT. 



high-pressure engine, the condenser and air-pump are suppressed, and the 
steam is allowed to escape at once from the cylinder into the atmosphere. 
It is obvious that in this arrangement the steam has to overcome the whole 
pressure of the air, and a much greater elastic force is required to produce 
the same effect ; but this is to a very great extent compensated by the absence 
of the air-pump and the increased simplicity of the whole machine. Large 
engines, both on shore and in steam-ships, are usually constructed on the 
condensing principle, the pressure seldom exceeding six or seven pounds per 
square inch above that of the atmosphere ; for small engines the high-pressure 
plan is, perhaps, preferable. Locomotive engines are of this kind. 

A peculiar modification of the steam-engine, employed in Cornwall for 
draining the deep mines of that country, is now getting into use elsewhere 
for other purposes. In this machine economy of fuel is carried to a most 
extraordinary extent, engines having been known to perform the duty of 
raising more than 100,000,000 lb. of water one foot high by the consumption 
of a single bushel of coals. The engines are single-acting ; the down-stroke, 
which is made against a vacuum, being the effective one, and employed to 
lift the enormous weight of the pump-rods in the shaft of the mine. When 
the piston reaches the bottom, the communication both with the boiler and 
the condenser is cut off, while an equilibrium-valve is opened, connecting the 
upper and lower extremities of the cylinder, whereupon the weight of the 
purnp-rods draws the piston to the top and makes the up-stroke. The engine 
is worked expansively, as it is termed, steam of high tension being emplo^ ed, 
which is cut off at one-eighth or even one-tenth of the stroke. 

The process of distillation, which may now be noticed, is very simple ; its 
object is either to separate substances which rise in vapour at different tem- 
peratures, or to part a volatile liquid from a substance incapable of volatili- 
sation. The same process applied to bodies which pass directly from the 
solid to the gaseous condition, and the reverse, is called sublimation. Every 
distillatory apparatus consists essentially of a boiler, in which the vapour is 
raised, and of a coudenser, in which it returns to the liquid or solid con- 
dition. In the still employed for manufacturing purposes, the latter is 
usually a spiral metal tube immersed in a tub of water. The common retort 
and receiver constitute the simplest and most generally useful arrangement 
for distillation on the small scale ; the retort is heated by a lamp or a char- 
rig. 35. 




II EAT. 



59 



coal fire, and the receiver is kept cool, if necessary, by a wet cloth, or it may 
be surrounded with ice. (Fig. 35.) 

Fie. 36 




The condenser of Professor Liebig is a very valuable instru- 
ment in the laboratory ; it consists of a glass tube (fig. 36), 
towering from end to end, fixed by perforated corks in the centre 
of a metal pipe, provided with tubes so arranged that a current 
of cold water may circulate through the apparatus. By putting 
a few pieces of ice into the little cistern, the temperature of this 
water may be kept at 32° (0°C), and extremely volatile liquids 
condensed. 

Liquids evaporate at temperatures below their boiling-points ; 
in this case the evaporation takes place solely from the surface. 
AVater, or alcohol, exposed in an open vessel at the temperature 
of the air, gradually dries up and disappears ; the more rapidly, 
the -warmer and drier the air above it. 

This fact was formerly explained by supposing that air and 
gases in general had the power of dissolving and holding in 
solution certain quantities of liquids, and that this power in- 
creased with the temperature ; such an idea is incorrect. 

If a barometer-tube (fig. 37) be carefully filled with mercury 
and inverted in the usual manner, and then a few drops of water 
passed up the tube into the vacuum above, a very remarkable 
effect will be observed; — the mercury will be depressed to a 
small extent, and this depression will increase with increase of 
temperature. Now, as the space above the mercury is void of 
air, and the weight of the few drops of water quite inadequate 
to account for this depression, it must of necessity be imputed 
to the vapour which instantaneously rises from the water into 
the vacuum ; and that this effect is really due to the elasticity 
or tension of the aqueous vapour, is easily proved by exposing 
the barometer to a heat of 212° (100°C), when the depression 
of the mercury will be complete, and it will stand at the same 
level within and without the tube, indicating that at that temper- 
ature the elasticity of the vapour is equal to that of the atmo- 
sphere, — a fact which the phenomenon of ebullition has already 
shown. 

By placing over the barometer a wide open tube dipping into the 
below, and then filling this tube with water at different temperat 



Fi*. 37 




mercury 
ures, the 



60 



II E A T 



tension of the aqueous vapour for each degree of the thermometer may be 
accurately determined by its depressing effect upon the mercurial column ; 
the same power which forces the latter doicn one inch against the pressure 
of the atmosphere, would of course elevate a column of mercury to the same 
height against a vacuum, and in this way the tension may be very conve- 
niently expressed. The following table was drawn up by Dr. Dalton, to 
whom we owe the method of investigation. 



Fig. 



Temperature. 
F. C. 

32° ... 0° . 


Tension in inches 
of mercury. 

0-200 

0-263 


Temperature. 
F. C. 

130° ... 54-4 . 
140 ... 60 . 
150 ... 65-5 . 
160 ... 71-1 . 
170 ... 76-6 . 
180 ... 82-2 . 
190 ... 87-7 . 
200 ... 93-3 . 
212 ...100 . 


Tension in inches 
of mercury. 

4-34 


40 ... 4-4 . 


5-74 


50 ... 10 . 
60 ... 15-5 . 


0-375 

0-524 

0-721 

1-000 


7-42 

9-46 


70 ... 21-1 . 
80 ... 26-6 . 


12-13 

15-15 


90 ... 32-2 . 


1-360 

1-860 

2-530 

3-330 


19-00 


100 ... 37-7 . 


23-64 


110 ... 43-3 . 


3000 


120 ... 48-8 . 






Other liquids tried in this manner are found to emit 
vapours of greater or less tension, for the same temper- 
ature, according to their different degrees of volatility: 
thus, a little ether introduced into the tube depresses the 
mercury 10 inches or more at the ordinary temperature 
of the air; oil of vitriol, on the other hand, does not 
emit any sensible quantity of vapour until a much greater 
heat is applied ; and that given off by mercury itself in 
warm summer weather, although it may by very delicate 
means be detected, is far too little to exercise any effect 
upon the barometer. In the case of water, the evapora- 
tion is quite distinct and perceptible at the lowest tem- 
peratures, when frozen to solid ice in the barometer-tube ; 
snow on 'the ground, or on a house-top, may often be 
noticed to vanish, from the same cause, day by day in the 
depth of winter, when melting was impossible. 

There exists for each vapour a state of density which 
it cannot pass without losing its gaseous condition, and 
becoming liquid ; this point is called the condition of 
maximum density. When a volatile liquid is introduced 
in sufficient quantity into a vacuum, this condition is 
always reached, and then evaporation ceases. Any at- 
tempt to increase the density of this vapour by com- 
pressing it into a smaller space will be attended by the 
liquefaction of a portion, the density of the remainder 
being unchanged. If a little ether be introduced into a 
barometer (fig. 38), and the latter slowty sunk into a xqvv 
deep cistern of mercury, it will be found that the height 
of the column of mercury in the tube above that in the 
cistern remains unaltered until the upper extremity of 
the barometer approaches the surface of the metal in the 
reservoir. It will be observed also, that, as the tube 
sinks, the little stratum of liquid ether increases in thick- 
ness, but no increase of elastic force occurs in the vapoar 
above it, and, consequently, no increase of density; for 
tension and density are always, under ordinary circum- 
stances at least, directly proportionate to each other in 
the same vapour. 



HEAT. 61 

The point of maximum density of a vapour is dependent upon the tem- 
perature ; it increases rapidly as the temperature rises. This is •well shown 
in the case of water. Thus, taking the specific gravity of atmospheric air 
at 212° (100°C) = 1000, that of aqueous vapour in its greatest possible 
state of compression for the temperature will be as follows : — 



Temperature. 
F. C. 

32° 0° 


Specific gravity. 
5-690 


"Weight of 100 cubic in( 
0-136 grains. 


50 10- 


10-293 


0-247 


60 15-5 , 


14-108 , 


0-338 


100 37-7 


46-500 


1-113 


150 65-5 

212 100 


170-293 

625-000 


4-076 

14-962 



The last number was experimentally found by M. Gay-Lussac ; the others 
are calculated upon that by the aid of Dr. Dalton's table of tensions. 

Thus, there are two distinct methods by which a vapour may be reduced 
to the liquid form ; pressure, by causing increase of density until the point 
of maximum density for the particular temperature is reached ; and cold, by 
which the point of maximum density is itself lowered. The most powerful 
effects are of course produced when both are conjoined. 

For example, if 100 cubic inches of perfectly transparent and gaseous 
vapour of water at 100° (37°-7C), in the state above described, had its tem- 
perature reduced to 50° (10°C), not less than 0-87 * grain of fluid water 
would necessarily separate, or very nearly eight-tenths of the whole. 

Evaporation into a space filled with air or gas follows the same law as 
evaporation into a vacuum ; as much vapour rises, and the condition of max- 
imum density is assumed in the same manner as if the space were perfectly 
empty ; the sole difference lies in the length of time required. When a 
liquid evaporates into a vacuum, the point of greatest density is attained at 
once, while in the other case some time elapses before this happens ; tho 
particles of air appear to oppose a sort of mechanical resistance to the rise 
of the vapour. The ultimate effect is, however, precisely the same. 

"When to a quantity of perfectly dry gas confined in a vessel closed by 
mercury, a little water is added, the latter immediately begins to evaporate, 
and after some time as much vapour will be found to have risen from it as 
if no gas had been present, the quantity depending entirely on the temper- 
ature to which the whole is subjected. The tension of this vapour will add 
itself to that of the gas, and produce an expansion of volume, which will be 
indicated by an alteration of level in the mercury. 

Vapour of water exists in the atmosphere at all times, and in all situa- 
tions, and there plays a most important part in the economy of nature. The 
proportion of aqueous vapour present in the air is subject to great variation, 
and it often becomes exceedingly important to determine its quantity. This 
is easily done by the aid of the foregoing principles. 

If the aqueous vapour be in its condition of greatest possible density for 
the temperature, or, as it is frequently, but most incorrectly expressed, the 
air be saturated with vapour of water, the slightest reduction of tempera- 
ture will cause the deposition of a portion in the liquid form. If, on the 
contrary, as is almost always in reality the case, the vapour of water be 
below its state of maximum density, that is, in an expanded condition, it is 
clear that a considerable fall of temperature may occur before liquefaction 
commences. The degree at which this takes place is called the dew-point, 

1 100 cubic inches aqueous Tapours at 100° (3T°-7C) ( weiehing 1-113 grain, wculd at, 50** 
(10°Cj, become reduced to 10-29 cubic inches, weighing 0-247 grain. 

6 



62 



HEAT. 



and it is determined with great facility by a very simple method. A little 
cup of thin tin-plate or silver, well polished, is tilled with water at the tem- 
perature of the air, and a delicate thermometer inserted. The water is then 
cooled by dropping in fragments of ice, or dissolving in it powdered sal- 
ammoniac, until a deposition of moisture begins to make its appearance on 
the outside, dimming the bright metallic surface. The temperature of the 
dew-point is then read off upon the thermometer, and compared with that 
of the air. 

Suppose, by way of example, that the latter were 70° (21°-1C), and the 
dew-point 50° (10°C) ; the elasticity of the watery vapour present would 
correspond to a 2-aximum density proper to 50° (10°C), and would support 
a column of mercury 0-375 inch high. If the barometer on the spot stood 
at 80 inches, therefore, 29-625 inches would be supported by the pressure 
of the dry air, and the remaining 0-375 inch by the vapour. Now a cubic 
foot of such a mixture must be looked upon as made up of a cubic foot of 
dry air, and a cubic foot of watery vapour, occupying the same space, and 
having tensions indicated by the numbers just mentioned. A cubic foot, or 
1728 cubic inches of vapour at 70° (21°-1C), would become reduced by con- 
traction, according to the usual law, to 1662-8 cubic inches at 50° (10°C) ; 
this vapour would be at its maximum density, having the specific gravity 
pointed out in the table ; hence 1662-8 cubic inches would weigh 4-11 grains. 
The weight of the aqueous vapour contained in a cubic foot of air will thus 
be ascertained. In England the difference between the temperature of 
the air and the dew-point seldom reaches 30° ( — 1°-2C) ; but in the Deecau, 
with a temperature of 90° (32°-2C), the dew-point has been seen as low as 
29° ( — 1°-6C) making the degree of dryness 61 °. 1 

Another method of finding the proportion of moisture present in the air 
is to observe the rapidity with which evaporation takes place, and which is 
always in some relation to the degree of dryness. The bulb 
of a thermometer is covered with muslin, and kept wet with 
water; evaporation produces cold, as will presently be seen, 
and accordingly the thermometer soon sinks below the ac- 
tual temperature of the air. Wheu it comes to rest, the 
degree is noticed, and from a comparison of the two tempe- 
ratures an approximation to the dew-point can be obtained 
by the aid of a mathematical formula contrived for the pur- 
pose. This is called the wet-bulb Irvgrometer ; it is often 
made in the manner shown in fig. 39, where one thermometer 
serves to indicate the temperature of the air, and the other 
to show the rate of evaporation, being kept wet by the 
thread in connexion with the little water reservoir. 

The perfect resemblance in every respect which vapours 
bear to permanent gases, led, very naturally, to the idea 
that the latter might, by the application of suitable means, 
be made to assume the liquid condition, and this surmise 
was, in the hands of Mr. Faraday, to a great extent verified. 
Out of the small number of such substances tried, not less 
than eight gave way ; and it is quite fair to infer, that, had 
means of sufficient power been at hand, the rest would have 
shared the same fate, and proved to be nflBiiug more than 
the vapours of volatile liquids in a state very far removed 
from that of their maximum density. The subjoined table 
represents the results of Mr. Faraday's first investigations, 

Mr. Li'.uk'll, Introduction to Chemical Philosophy, p. lbi. 



Fig. 39. 




HEAT. Od 

■with the pressure in atmospheres, and the temperature at which the con- 
iensation took place. 1 

Atmospheres. 

Sulphurous acid 2 

Sulphuretted hydrogen 17 

Carbonic acid 36 

Chlorine 4 

Nitrous oxide 50 

Cyanogen 3-6 

Ammonia 6-5 

Hydrochloric acid 40 

The method of proceeding was very simple ; the materials were sealed up 
in a strong narrow tube (fig. 40), together with a little pressure-gauge, con- 
Fig. 40. 



Temperature. 


F. 


0. 




. 45° 


7° 


•2 


, 50 


10 




. 32 







. 60 


15 


•5 


. 45 


7 


•2 


. 45 


7 


•2 


. 50 


10 




. 50 


10 






sisting of a slender tube closed at one end, and having within it, near the 
open extremity, a globule of mercury. The gas being disengaged by the 
application of heat, or otherwise, accumulated in the tube, and by its own 
pressure brought about condensation. The force required for this purpose 
was judged of by the diminution of volume of the air in the gauge. 

Mr. Faraday has since resumed, with the happiest results, the subject of 
the liquefaction of the permanent gases. By using narrow green glass tubes 
of great strength, powerful condensing syringes, and an extremely low tem- 
perature, pix)duced by means to be presently described, olefiant gas, hydri- 
odic and hydrobromic acids, phosphoretted hydrogen, and the gaseous 
fluorides of silicon and boron, were successively liquefied. Oxygen, hydro- 
gen, nitrogen, nitric oxide, carbonic oxide, and coal-gas, refused to liquefy 
at the temperature of — 166° ( — 74°-4C) while subjected to pressures vary- 
ing in the different cases from 27 to 58 atmospheres. 3 

Sir Isambard Brunei, and, more recently, M. Thilorier, of Paris, suc- 
ceeded in obtaining liquid carbonic acid in great abundance. The apparatus 
of M. Thilorier (fig. 41) consists of a pair of extremely strong metallic ves- 
sels, one of which is destined to serve the purpose of a retort, and the other 
that of a receiver. They are made either of thick cast-iron or gun-metal, 
or, still better, of the best and heaviest boiler-plate, and are fnrnished with 
stop-cocks of a peculiar kind, the workmanship of which must be excellent. 
The generating vessel or retort has a pair of trunnions upon which it swings 
in an iron frame. The joints are secured by collars of lead, and every pre- 
caution taken to prevent leakage under the enormous pressure the vessel 
has to bear. The receiver resembles the retort in every respect ; it has a 
similar stop-coci, and is connected with the retort by a strong copper tube 
and a pair of miion screw-joints; a tube passes from the stop-cock down- 
wards, and terminates near the bottom of the vessel. 

The operation is thus conducted : 2| lb. of bicarbonate of soda, and 6j 
lb. of water at 100° (37°-7C), are introduced into the generator ; oil of vitriol 

1 Phil. Trans, for 1823, p. 189. 

2 Phil. Trans, for 1845, p. 155, 



<>4 




to the amount of 1 J lb. is poured into a copper cylindrical vessel, which is 
lowered down into the mixture, and set upright ; the stop-cock is then 
screwed into its place, and forced home by a spanner and mallet. The ma- 
chine is next tilted up on its trunnions, that the acid may run out of the 
cylinder and mix with the other contents of the generator ; and this mixture 
is favoured by swinging the whole backwards and forwards for a few mi- 
nutes, after which it may be suffered to remain a little time at rest. 

The receiver, surrounded with ice, is next connected to the generator, and 
both cocks opened ; the liquefied carbonic acid distils over into the colder 
vessel, and there again in part condenses. The cocks are now closed, the 
vessels disconnected, the cock of the generator opened to allow the contained 
gas to escape ; and, lastly, when the issue of gas has quite ceased, the stop- 
cock itself unscrewed, and the sulphate of soda turned out. This operation 
must be repeated five or six times before any very considerable quantity of 
liquefied acid will have accumulated in the receiver. When the receiver 
thus charged has its stop-cock opened, a stream of the liquid is forcibly 
driven up the tube by the elasticity of the gas contained in the upper part 
of the vessel. 

It will be quite proper to point out to the experimenter the great personal 
danger he incurs iu using this apparatus, unless the greatest care be taken 
in its management. A dreadful accident has already occurred in Paris by 
the bursting of one of the iron vessels. 

The cold produced by evaporation has been already adverted to; it is 
simply an effect arising from the conversion of sensible heat into latent by 
the rising vapour, and it may be illustrated in a variety of ways. A little 
ether dropped on the hand thus produces the sensation of great cold, and 
■water contained in a thin glass tube, surrounded by a bit of rag, is speedily 
frozen when the rag is kept wetted with ether. 



HEA 



65 



Fig. 42. 




When a little water is put into a watch-glass, 
(fig. 42), supported by a triangle of wire over 
a shallow glass dish of sulphuric acid placed 
on the plate of a good air-pump, the whole 
covered with a low receiver, and the air with- 
drawn as perfectly as possible, the water is in 
a few minutes converted into a solid mass of ice, 
and the watch-glass very frequently broken by 
the expansion of the lower portion of water in 
the act of freezing, a thick crust first forming on the surface. The absence 
of the impediment of the air, and the rapid absorption of watery vapour by 
the oil of vitriol, induce such quick evaporation that the water has its tem- 
perature almost immediately reduced to the freezing-point. 

The same fact is shown by a beautiful instrument contrived by Dr. Wol- 
laston, called a cryophorus, or frost-carrier. It is made of glass, of the form 
represented in fig. 43, and contains a small quantity of water, the rest of 
the space being vacuous. When all the water is turned into the bulb, and 
the empty extremity plunged into a mixture of ice and salt, the solidification 
of the vapour gives rise to such a quick evaporation from the surface of the 
water, that the latter freezes. 

Tig. 43. 




Fig. 44. 



All means of producing artificial cold yield to that derived from the 
povation of the liquefied carbonic acid, just mentioned. When a jet of 
liquid is allowed to issue into the air from a nar- 
row aperture, such an intense degree of cold is 
produced by the vaporization of a part, that the 
remainder freezes to a solid, and falls in a shower 
of snow. By suffering this jet of liquid to flow into 
a metal box provided for the purpose, shown in the 
drawing of the apparatus (fig. 44), a large quantity 
of the solid acid may be obtained ; it closely re- 
sembles snow in appearance, and when held in the 
hand occasions a painful sensation of cold, while 
it gradually disappears. Mixed with a little ether, 
and poured upon a mass of mercury, the latter 
is almost instantly frozen, and in this way pounds 
of the solidified metal may be obtained. The addi- 
tion of the ether facilitates the contact of the car- 
bonic acid with the mercury. 

The temperature of a mixture of solid carbonic 
acid and ether in the air, measured by a spirit- 
thermometer, was found to be — 106° ( — 76° -GC) ; 
when the same mixture was placed beneath the 
receiver of an air-pump, and exhaustion rapidly 
made, the temperature sank to — 166° ( — 110°C). 
This was the method of obtaining extreme cold 
employed by Mr. Faraday in his last experiments 
on the liquefaction of gases. Under such circum- 
6* 



eva- 
that 




36 HEAT. 

stances, the liquefied hydriodic, hydrobromic, and sulphurous acid gases, 
carbonic acid, nitrous oxide, sulphuretted hydrogen, cyanogen, and ammo 
nia, froze to colourless transparent solids, and alcohol became thick and oily. 
The principle of the cryophorus has been very happily applied by Mr. 
Daniell to the construction of a dew-point hygrometer : fig. 44. It consists 
of a bent glass tube terminated by two bulbs, one of which is half filled with 
ether, the whole being vacuous as respects atmospheric air. A delicate ther- 
mometer is contained in the longer limb, the bulb of which dips into the 
ether ; a second thermometer on the stand serves to show the actual tempe- 
rature of the air. The upper bulb is covered with a bit of muslin. When 
an observation is to be made, the liquid is all transferred to the lower bulb, 
and ether dropped upon the upper one, until by the cooling effects of evapo- 
ration a distillation of the contained liquid takes place from one part of the 
apparatus to the other, by which such a reduction of temperature of the 

flier is brought about, that dew is deposited on the outside of the bulb, which 
made of black glass in order that it may be more easily seen. The differ- 
ence of temperature indicated by the two thermometers is then read off. 

CAPACITY FOR HEAT ; SPECIFIC HEAT. 

Let the reader renew a supposition made when the doctrine of latent heat 
was under consideration; let him imagine the existence of an uniform source 
of heat, and its intensity such as to raise a given weight of water 10° 
(5°-5C) in 80 minutes. If, now, the experiment be repeated with equal 
weights of mercury and oil, it will be found, that instead of 30 minutes, 1 
minute will suffice in the former case, and 15 minutes in the latter. 

This experiment serves to point out the very important fact, that different 
bodies have different capacities for heat; that equal weights of water, oil, 
and mercury, require, in order to rise through the same range of tempera- 
ture, quantities of heat in proportion of the numbers 80, 15, and 1. This 
is often expressed by saying that the specific heat of water is 30 times as 
great as that of mercury, and the specific heat of oil 15 times as great. 

Again, if equal weights of water at 100° (37°-7C), and oil at 40° (4°-4C), 
be agitated together, the temperature of the whole will be found to be 80° 
(l!(j°-GC), instead of 70° (21°-1C), the mean of the two ; and if the tempera- 
tures be reversed, that of the mixture will be only 60° (15° -5C). Thus, 

1 lb. water at 100° (37°-7C) ) . . , , 0rt „ , OCn rn . , 

1 lb. oil at 40° (4<MC) f glve a mixture at 80 ( 26 °- 6 C) ; hence 
Loss by the water, 20° (11°-1C). 
Gain by the oil, 40° (22°-2C). 

1 lb. water at 40° (4°-4C) ~| . . , . rno nro rn , , 

1 lb. oil at 100° (37-7C) } glve a mixture at G0 ( 15 5C ) ' lience 
Gain of water, 20° (11°-1C). 
Loss of oil, 40° (22°-2C). 

This shows the same fact, that water requires twice as much heat as oil to 
produce the same thermometric effect. 

There are three distinct methods by which the specific heat of various 
nbstances may be estimated. The first of these is by observing the quantity 
f ice melted by a given weight of the substance heated to a particular tem- 
perature; the second is by noting the time which the heated body requires 
to cool down through a certain number of degrees; and the third is the 
method of mixture, on the principle illustrated ; this latter method is pre- 
ferred as the most accurate. 

The determination of the specific heat of different substances has occupied 
the attention of many experimenters; among these MM, Dulong and Petit, 
and recently M. Regnault, deserve especial mention. It appears that each 
solid and Ikjuid has its own specific heat; and it is probable that this, in- 



n e a t . 67 

(stead of being a constant quantity, varies with the temperature. The de- 
termination of the specific heat of gases is attended with peculiar difficulties 
on account of the comparatively large volume of small weights of gases. 
Satisfactory results have however been obtained by the method of mixing for 



SPECIFIC HEAT AT 30 INCHES PRESSURE. 
Of equal volumes. Of equal -weights. 

Air = 1 Water ■== 1 

Atmospheric air 1 1 0-2669 

Oxygen 1 0-8848 0-2361 

Hydrogen 1 12-3401 3-2936 

Nitrogen 1 1-0318 0-2754 

Carbonic oxide 1 1-0805 0-2884 M 

Protoxide of pitrogen... 1-227 0-8878 0-2369 

Carbonic acid 1-249 0-8280 0-2210 

defiant gas 1-754 1-5763 0-4207 

Aqueous vapour 1-960 3-1360 0-8470 1 

For the comparison of the specific heat of atmospheric air with that of 
water, we are indebted to Count Rumford ; for the comparison of the specific 
heat of the various gases, to Delaroche and Berard. 

Whenever a gas expands, heat becomes thereby latent. Hence the amount 
of heat required to raise a gas to a certain temperature increases the more 
we allow it to expand. Dulong has found that if the amount of heat re- 
quired to raise the temperature of a volume of gas (observed at the melting 
point of ice, and at the pressure of 30 inches) to a given height without its 
volume undergoing any change, be represented by 1, then if the gas is al- 
lowed to expand until the pressure is reduced again to 30 inches whilst the 
high temperature is kept up, the additional amount of heat which is required 
for this purpose is, for oxygen, hydrogen, or nitrogen 0,421 ; for carbonic 
acid 0,423 ; for binoxide of nitrogen 0,343 ; and for olefiant gas 0,240. 

If there be no source of heat from which this additional quantity can be 
obtained, then the gas is cooled during expansion, a portion of the free heat 
becoming latent. On the other hand, if a gas be compressed, this latent 
heat becomes free, and causes an elevation of temperature, which, under 
favourable circumstances, may be raised to ignition ; syringes by which 
tinder is kindled are constructed on this principle. In the upper regions of 
the atmosphere the cold is intense ; snow covers the highest mountain-tops 
even within the tropics, and this is due to the increased capacity for heat of 
the expanded air. 

MM. Dulong and Petit observed in the course of iheir investigation a most 
remarkable circumstauce. If the specific heats of bodies be computed upon 
equal weights, numbers are obtained, all different, and exhibiting no simple 
relations among themselves ; but if, instead of equal weights, quantities be 
taken in the proportion of the chemical equivalents, an almost perfect coin- 
cidence in the numbers will be observed, showing that some exceedingly in- 
timate connexion must exist between the relations of bodies to heat and 
their chemical nature ; and when the circumstance is taken into view, that 
relations of even a still closer kind link together chemical and electrical 
phenomena, it is not too much to expect that ere long some law may be dis- 
covered far more general than any with which we are yet acquainted. 

1 The later determinations of Pveguault vary from the above: thus in equal ^eights, 
TTater = l; Atmospheric air he gives as 0-2377; Oxygen, 0-2182; Nitr'vgen, 02440; and 
Vapour of Water, 0-1750; and contrary to the results of Uay-Lussac, the specific heat of aix 
does not vary with the temperature. — R. B. 



68 HEAT. 

The following table is extracted from the memoirs of M. Regnault, witii 
"whose results most of the experiments of Dulong and Petit closely coincide 

Substances. Specific heat of Specific heat of 

equal weights. equivalent weights. 

Water 1-00000 

Oil of Turpentine 0-42593 

Glass 0-19768 

Iron 0-11379 3-0928 

Zinc 0-09555 3-0872 

Copper 0-09515 3-0172 

Lead 0-03140 3-2581 

Tin 0-05623 3-3121 

Nickel 010863 3-2176 

Cobalt 0-10696 3-1628 

Platinum 0-03243 3-2054 

Sulphur 0-20259 3-2657 

Mercury 0-03332 3-7128 

Silver 0-05701 6-1742 

Arsenic 0-08140 6-1326 

Antimony 005077 6-5615 

Gold 0-03244 6-4623 

Iodine 0-05412 6-8462 

Bismuth 0-03084 2-1877 

Of the numbers in the second column, the first ten approximate far too 
closely to each other to be the result of mere accidental coincidence ; the five 
that follow are very nearly twice as great; and the last is one-third less. 1 

Independently of experimental errors, there are many circumstances 
which tend to shoAV, that, if all modifying causes could be compensated, or 
their effects allowed for, the law might be rigorously true. 

The observations thus made upon elementary substances have been ex- 
tended by M. Regnault to a long series of compounds, and the same curious 
law found, with the above limitations, to prevail throughout, save in a few 
isolated cases, of which an explanation can perhaps be given. 

Except in the case of certain metallic alloys, where the specific heats were 
the mean of those of their constituent metals, no obvious relation can be 
traced between the specific heat of the compound body and of its compo- 
nents. The most general expression of the facts that can be given is the 
following : — 

In bodies of similar chemical constitution, the, specific heats are in an inverse 
ratio to the equivalent weights, or to a multiple or submulfiple of the latter. — 
Simple as well as compound bodies will be comprehended in this law. 3 

SOURCES OF HEAT. 

The first and greatest source of heat, compared with which all others are 
totally insignificant, is the sun. The luminous rays are accompanied by 
rays of a heating nature, which, striking against the surface of the earth, 
elevate its temperature; this heat is communicated to the air by convection, 
ns already described, air and gases in general not being sensibly heated by 
the passage of the rays. 

: The equivalent of Bismuth being assumed as 71. but adopting 213. the number given 
tinder the head of bismuth, the specific heat of an equivalent weight will be G'oOSS, or coiu- 
Cido with the five preceding. — R. lb 

9 Ann. Cbim. et Phys. lxxiii. 5; and the same, 3rd series, i. 129. 



HEAT. 69 

A second source of heat is supposed to exist in the interior of the earth. 
It has been observed, that in sinking mine-shafts, boring for water, &c, the 
temperature rises in descending, at the rate, it is said, of about 1° (|-°C) for 
every 45 feet, or 117° (65°C) per mile. On the supposition that the rise 
continued at the same rate, at the depth of less than two miles the earth 
would have the temperature of boiling water ; at nine miles it would be red 
hot ; and at 30 or 40 miles depth, all known substances would be in a state 
of fusion. 1 

According to this idea, the earth must be looked upon as an intensely- 
heated, fluid spheroid, covered with a crust of solid badly-conducting mat- 
ter, cooled by radiation into space, and bearing somewhat the same propor- 
tion in thickness to the ignited liquid within, that the shell of an egg does 
to its fluid contents. Without venturing to offer any opinion on this theory, 
it may be sufficient to observe that it is not positively at variance with any 
kuowu fact; that the figure of the earth is really such as would be assumed 
by a fluid mass ; and, lastly, that it offers the best explanation we have of 
the phenomena of hot springs and volcanic eruptions, and agrees with the 
chemical nature of their products. 

The smaller, and what may be called secondary, sources of heat, are very 
numerous ; they may be divided, for the present, into two groups, me- 
chanical motion and chemical combination. To the first must be referred ele- 
vation of temperature by friction and blows ; and to the second, the effects of 
combustion and animal respiration. "With regard to the heat developed by 
friction, it appears to be indefinite in amount, and principally dependent 
upon the nature of the rubbing surfaces. An experiment of Count Bnrnford 
is on record, in which the heat developed by the boring of a brass cannon 
was sufficient to bring to the boiling-point two and a half gallons of water, 
while the dust or shavings of metal, cut by the borer, weighed a few ounces 
only. Sir H. Davy melted two pieces of ice by rubbing them together in 
vacuo at 32° (0°C) ; and uncivilized men, in various parts of the world, have 
long been known to obtain fire by rubbing together two pieces of dry wood. 
The origin of the heat in these cases is by no means intelligible. 

Malleable metals, as iron and copper, which become heated by hammering 
or powerful pressure, are found thereby to have their density sensibly 
increased and their capacity for heat diminished ; the rise of temperature is 
thus in some measure explained. A soft iron nail may be made red-hot by 
a few dexterous blows on an anvil ; but the experiment cannot be repeated 
until the metal has been annealed, and in that manner restored to its original 
physical state. 

The disengagement of heat in the act of combination is a phenomenon of 
the utmost generality. The quantity of heat given out in each particular 
case is in ail probability fixed and definite ; its intensity is dependent upon 
the time over which the action is extended. Science has already been en- 
riched by many admirable, although yet incomplete, researches on this im- 
portant but most difficult subject. 



It is not improbable that many of the phenomena of heat, classed at present 
under different heads, may hereafter be referred to one common cause, 
namely, alterations in the capacity for heat of the same body under different 

1 The new Artesian well at Grenelle. near Paris, has a depth of 1794 , 5 English feet: it is 
"bored through the chalk basin to the sand beneath : the work occupied seven years and two 
months. The temperature of the water, which is exceedingly abundant, is 82° (27°-7C) ; th» 
mean temperature of Paris is 51° (10°oC); the difference is 31° (17°"2C), which gives a rate 
of about 1° (|QC) for 58 feet. 



70 HEAT. 

physical conditions. For example, the definite absorption and evolution of 
sensible heat attending change of state may be simply due to the increased 
capacity for heat, to a fixed and definite amount, of the liquid over the solid, 
and the vapour over the 'liquid. The experimental proof of the facts is yet 
generally wanting; in the very important case of water, however, the deci- 
dedly inferior capacity for heat of ice compared with that of liquid water 
seems fully proved from experiments on record. 

The heat of combination might perhaps, in like manner, be traced to con- 
densation of volume, and the diminution of capacity for heat which almost 
invariably attends condensation. The proof of the proposition in numerous 
cases would be within the reach of comparatively easy experimental inquiry. 



LIGHT. 71 



LIGHT. 

The subject of light is so little connected with elementary chemistry, that 

very slight notice of some of the most important points "will suffice. 

Two views have been entertained respecting the nature of light. Sir 
Isaac Newton imagined that luminous bodies emitted, or shot out, infinite!}' 
small particles in straight lines, which, by penetrating the transparent part 
of the eye and falling upon the nervous tissue, produced vision. Other phi- 
losophers drew a parallel between the properties of light and those of sound, 
and considered, that as sound is certainly the effect of undulations, or little 
waves, propagated through elastic bodies in all directions, so light might be 
nothing more than the consequence of similar undulations transmitted with 
inconceivable velocity through a highly elastic medium, of excessive tenuity, 
filling all space, and occupying the intervals between the particles of mate- 
rial substances, to which they gave the name of ether. The wave-hypothesis 
of light is at present most in favour, as it serves to explain certain singular 
phenomena, discovered since the time of Newton, with greater facility than 
the other. 

A ray of light emitted from a luminous body proceeds in a straight line, 
and with extreme velocity. Certain astronomical observations afford the 
means of approximating to a knowledge of this velocity. The satellites of 
Jupiter revolve about the planet in the same manner as the moon about the 
earth, and the time required by each satellite for the purpose, is exactly 
known from its periodical entry into or exit from the shadow of the planet. 
The time required by one is only 42 hours. Komer, the astronomer, at 
Copenhagen, found that this period appeared to be longer when the earth, in 
its passage round the sun, was most distant from the planet Jupiter, and, 
on the contrary, he observed that the periodic time appeared to be shorter 
when the earth was nearest to Jupiter. The difference, though very small, 
for a single revolution of the satellite, by the addition of many, so increases, 
during the passage of the earth from its nearest to its greatest distance 
from Jupiter, that is, in about half a year, that it amounts to 16 minutes 
and 16 seconds. Romer concluded from this, that the light of the sun 
reflected from the satellite, required that time to pass through a distance 
equal to the diameter of the orbit of the earth, and since this space is little 
short of 200 millions of miles, the velocity of light cannot be less than 200,000 
miles in a second of time. It will be seen hereafter that this rapidity of 
transmission is rivalled by that of the electrical agent. 

When a ray of light falls on a plane surface it may be disposed of m three 
ways; it may be absorbed and disappear altogether; it may be reflected, or 
thrown off, according to a particular law ; or it may be partly absorbed, 
partly reflected, and partly transmitted. The first happens when the surface 
is perfectly black and destitute of lustre ; the second, when a polished surface 
of any kind is employed; and the third, when the body upon which the light 
falls is of the kind called transparent, as glass or water. 

The law of reflection is extremely simple. If a line be drawn perpendi- 
cular to the surface upon which the ray falls, and the angle contained 
between the ray and the perpendicular measured, it will be found that the 
ray, after reflection, takes such a course as to make with the perpendiculai 



72 



LIGHT. 




Fig. 46. 



yg 



an equal angle on the opposite of the latter. A ray of light, r, fig. 45, 

falling at the point p, -will be reflected in 
the direction pr', making the angle k / pp / 
equal to the angle kpp 7 ; or a ray from 
the point r falling upon the same spot will 
be reflected to r f in virtue of the same 
law. Farther, it is to be observed, that 
the incident and reflected rays are always 
contained in the same vertical plane. 

The same rule holds good if the mirror 

be curved, as a portion of a sphere, the 

curve being considered as made up of a 

multitude of little planes. Parallel rays 

become permanently altered in direction when reflected from curved surfaces, 

becoming divergent or convergent according to the kind of curvature. 

It has just been stated that light passes in straight lines ; but this is only 
*-rue so long as the medium through which it travels preserves the same 
density and the same chemical nature ; when this ceases to be the case, the 

ray of light is bent from its course 
into a new one, or, in optical lan- 
guage, is said to be refracted. 

Let r, fig. 46, be a ray of light 
falling upon a plate of some trans- 
parent substance with parallel sides, 
such as a piece of thick plate glass ; 
and a its point of contact with the 
upper surface. The ray, instead 
of holding a straight course and 
passing into the glass in the direc- 
tion a b, will be bent downwards 
to c ; and, on leaving the glass, and issuing into the air on the other side, 
it will again be bent, but in the opposite direction, so as to make it parallel 
to the continuation of its former track. The general law is thus expressed : 
— When the ray passes from a rare to a denser medium, it is usually refracted 
towards a line perpendicular to the surface of the latter ; and conversely, 
when it leaves a dense medium for a rarer one, it is refracted from a line 
perpendicular to the surface of the denser substance : in the former case 
the angle of incidence is said to be greater than that of refraction ; in the 
latter, it is said to be less. 

The amount of refraction, for the same medium, varies with the obliquity 
with which the ray strikes the surface. When 
perpendicular to the latter, it passes without 
change of direction at all; and in other posi- 
tions, the refraction increases with the obli- 
quity. 

Let e, fig. 47, represent a ray of light fall- 
ing upon the surface of a mass of plate glass 
at the point a. From this point let a perpen- 
dicular be raised and continued into the new 
medium, and around the same point, as a 
centre, let a circle be drawn. According to 
the law just stated, the refraction must be to- 
wards the perpendicular ; in the direction ah/ 
for example. Let the lines a — a, a / — a', at 
right angles to the perpendicular, be drawn, 
and their length compared by means of a scale of equal parts, and noted ; 



rig. 4r, 




LIGHT. 



73 



their length will be in the case supposed in the proportion of 3 to 2. These 
lines are termed the sines of the angles of incidence and refraction, re- 
spectively. 

Now let another ray be taken, such as r ; it is refracted in the same man~ 
ner to r / , the bending being greater from the increased obliquity of the ray ; 
but what is very remarkable, if the sines of the two new angles of inci- 
dence and refraction be again compared they will still be found to bear to 
each other the proportion of 3 to 2. The fact is expressed by saying, that 
the ratio of the sines of the incidence and refraction is constant for the same 
medium. 

The plane of refraction coincides moreover with that of incidence. 

Different bodies possess different refractive powers ; generally speaking, 
the densest substances refract most. Combustible bodies have been noticed 
to possess greater refractive power than their density would indicate, and 
from this observation Sir I. Newton predicted the combustible nature of the 
diamond long before anything was known respecting its chemical nature. 

The method adopted for describing the comparative refractive powers of 
different bodies is to state the ratio borne by the sine of the angle of refrac- 
tion to that of incidence, making the former unity : this is called the index 
of refraction for the substance. Thus, in the case of glass, the index of re- 
fraction will be 1-5. When this is once known for any particular transparent 
body, the effect of the latter upon a ray of light entering it, in any position, 
can be calculated by the aid of the law of sines. 



Substances. 
Tabasheer ' 

Ice 

"Water 



Index of refraction. 

1-10 

1-30 

1-34 



Fluor spar 1-40 

Plate glass 1-50 

Rock ci-ystal 1-60 

Crysolite 1-69 

Bisulphide of carbon 1-70 



Substances. Index of refraction. 

Garnet 1-80 

Glass, with much oxide 

of lead 1-90 

Zircon 2-00 

Phosphorus 2-20 

Diamond 2-50 

Chromate of lead 3-00 



Pig. 48. 




When a luminous ray enters a mass of substance differing in refractive 
power from the air, and whose surfaces are not parallel, it becomes perma- 
nently deflected from its course and altered in its 
direction. It is upon this principle that the pro- 
perties of prisms and lenses depend. To take 
an example. — Let fig. 48 represent a triangular 
prism of glass, upon the side of which the ray 
of light r may be supposed to fall. This ray 
will of course be refracted in entering the glass 
towards a line perpendicular to the first surface, 
and again, from a line perpendicular to the 

second surface on emerging into the air. The result will be a total change 
in the direction of the ray. 

A convex lens is thus enabled to converge rays of light falling upon it, 
and a concave lens to separate them more wideh T ; each separate part of the 
surface of the lens producing its own independent effect. 

The light of the sun and celestial bodies in general, as well as that of +he 
elective spark, and of all ordinary flames, is of a compound nature. If a ray 
of light from any of the sources mentioned be admitted into a dark room by a 
small hole in the shutter, or otherwise (fig. 49), and suffered to fall upon a 



1 A siliceous deposit in the joints of the bamboo. 



74 







glass prism in the manner described above, it will not only be refracted from 
its straight course, but will be decomposed into a number of coloured rays, 
which may be received upon a white screen placed behind the pi'ism. When 
solar light is employed, the colours are extremely brilliant, and spread into 
an oblong space of considerable length. The upper part of this image or 
spectrum will be violet, and the lower red, the intermediate portion, com- 
mencing from the violet, being indigo, blue, green, yellow, and orange, all 
graduating imperceptibly into each other. This is the celebrated experiment 
of Sir I. Newton, and from it he drew the inference that white light is com- 
posed of seven primitive colours, the rays of which are differently refran- 
gible by the same medium, and hence capable of being thus separated. The 
violet rays are most refrangible, and the red rays least. 

Sir D. Brewster is disposed to think, that out of Newton's seven primitive 
colours four are really compound, and formed by the superposition of the 
three remaining, namely, blue, yellow, and red, which alone deserve the 
name of primitive. When these three kinds of rays are mixed, or super- 
imposed, in a certain definite manner, they produce white light, but when 
one or two of them are in excess, then an effect of colour is perceptible, 
pimple in the first case, and compound in the second. There are, according 
to this hypothesis, rays of all refrangibilities of each colour, and conse- 
quently white light in every part of the spectrum, but then they are une- 
qually distributed ; the blue rays are more numerous near the top, the yel- 
low towards the middle, and the red at the bottom, the excess of each colour 
producing its characteristic effect. In the diagram below (fig. 50) the inten- 
sity of each colour is represented by the height of a curve, and the effects 
of mixture will be intelligible by a little consideration. 



Fig. 50. 
YELLOW. RED. 



SOLAR SPECTRUM. 




Bodies of the same jnean refractive power do not always equally disperse 
or spread out the differently coloured rays; because the principal yellow or 
red rays, for instance, are equally refracted by two prisms of different ma- 
terials, it does not follow that the blue or the violet shall be similarly 
affected. Hence, prisms of different varieties of glass, or other transparent 
substances, give, under similar circumstances, very different spectra, both 



LIGHT. 75 

as respects the length of the image, and the relative extent of the coloured 
bands. 

The colours of natural objects are supposed to result from the power 
which the surfaces of the bodies possess of absorbing some of the coloured 
rays, while they reflect or transmit, as the case may be, the remainder. 
Thus, an object appears red because it absorbs, or causes to disappear, a 
portion of the yellow and blue rays composing the white light by which it is 
illuminated. 

A ray of common light made to pass through certain crystals of a par- 
ticular order is found to undergo a very remarkable change. It becomes 
split or divided into two rays, one of which follows the general law of refrac- 
tion, and the other takes a new and extraordinary course, dependent on the 
position of the crystal. This effect, which is called double refraction, is 
beautifully illustrated in the case of Iceland spar, or crystallized carbonate 
of lime. On placing a rhomb of this substance on a piece of white paper, 
on which a mark or line has been made, the object will be seen double. 

Again, if a ray of light be suffered to fall upon a plate of glass at an angle 
of 56° 45 / , the portion of the ray which suffers reflection will be found to 
have acquired properties which it did not before possess ; for on throwing 
it, under the same angle, upon a second glass plate, it will be observed that 
there are two particular positions of the latter in which the ray ceases to 
be reflected. Light which has suffered this change is said to be polarized. 

The light which passes through the first or polarizing 
plate, is also to a certain extent in this peculiar condi- 
tion, and by employing a series of similar plates (fig. 51), 
held parallel to the first, this effect may be greatly in- 
creased ; a bundle of fifteen or twenty such plates may 
be used with great convenience for the experiment. It is 
to be remarked, also, that the light polarized by trans- 
mission in this manner is in an opposite state to that 
polarized by reflection ; that is, when examined by a 
second or analyzing plate, held at the angle before men- 
tioned, it will be seen to be reflected when the other dis- 
appears, and to be absorbed when the first is reflected. 

It is not every substance which is capable of polarizing 
light in this manner; glass, water, and certain other bo- 
dies, bring about the change in question, each having a 
particular polarizing angle at which the effect is greatest. The metals also 
can, by reflection, polarize the light, but they do so very imperfectly. The 
two rays into which a pencil of common light divides itself in passing 
through a doubly-refracting crystal are found on examination to be polarized 
in a very complete manner, and also transversely, the one being capable of 
reflection when the other vanishes. It is said that both rays are polarized 
in opposite directions. With a rhomb of transparent Iceland spar of toler- 
ably large dimensions the two oppositely-polarized rays may be widely sepa- 
rated and examined apart. 

There is yet another method of polarization, by the employment of plates 
of the mineral tourmaline cut parallel to the axis of the crystal. This body 
polarizes by simple transmission, the ray falling perpendicular to its surface ; 
a part of the light is absorbed, and the remainder modified in the manner 
described. When two such plates are held with their axes parallel, as in 
fig. 52, light traverses them both freely ; but when one of them is turned 
round in the manner shown in fig. 53, so as to make the axes cross at right 
angles, the light is almost wholly stopped, if the tourmalines be good. A 
plate of the mineral thus becomes an excellent test for discriminating be- 
tween the polarized light and that which has not undergone the change. 
Some of the most splendid phenomena of the science of light are exhibited 




76 



LIGHT. 



Fig. 52. 



Fig. 53. 





when tliin plates of doubly-refracting substances are interposed between the 
polarizing arrangement and the analyzer. 

Instead of the tourmaline plate, which is always coloured, frequent use 
is made of two Nichol's prisms, or conjoined prisms of carbonate of lime, 
which, in consequence of a peculiar cutting and combination, possess the 
property of allowing only one of the oppositely polarized rays to pass. If 
the two Nichol's prisms are placed one behind the other in precisely similar 
positions, the light polarized by the one goes through the other unaltered. 
But when one prism is slightly turned round in its setting, a cloudiness is 
produced, and by continuing to turn the prism this increases until perfect 
darkness ensues. This happens, as with the tourmaline plates, when the 
two prisms cross one another. The phenomenon is the same with colourless 
as with coloured light. 

Supposing that polarized light, coloured, for example, by going through a 
plate of red glass, passed through the first Nichol's prism and was altogether 
obstructed in consequence of the position of the second prism, then if be- 
tween the two prisms a plate of rock crystal, formed by a section at right 
angles to the principal axis of the crystal, is interposed, the light polarized 
by the first prism by passing through the plate of quartz is enabled par- 
tially to pass through the second Nichol's prism. Its passage through the 
second prism can then again be interrupted by turning the second prism 
round to a certain extent. The rotation required varies with the thickness 
of the plate of rock crystal, and also with the colour of the light that is 
employed. It increases from red in the following order, green, yellow, blue, 
violet. 

This property of rock crystal was discovered by Arago. The kind of 
polarization has been called circular polarization. No other crystals are 
known to produce the same effect. The direction of the rotation is with 
many plates towards the right hand ; in other plates it is towards the left. 
The one class is said to possess right-handed polarization ; the other class 
left-handed polarization. 

Biot observed that many solutions of organic substances exhibit the pro- 
perty of circular polarization, though to a far less extent than rock crystal. 
Thus, solution of cane-sugar and tartaric acid possess right-handed polari- 
zation, whilst albumen, grape-sugar, and oil of turpentine, are left-handed. 
In all these solutions the amount of circular polarization increases with the 
concentration of the fluid and the thickness of the column of liquid through 
which the light passes. Hence circular polarization is an important auxiliary 
in chemical analysis. In order to determine the amount of polarization 
which any fluid exhibits, the liquid is put into a glass tube not less than 
from ten to twelve inches long, which is closed with glass plates, one of 
which should be coloured, red for example. This is then placed between 
the two Nichol's prisms, which have previously been so arranged with regard 
to each other that no light could pass through. An apparatus of this de- 
scription, the saccharometer, is chiefly used for determining the concentra- 
tion of solutions of sugar. 



l i a ii t . 77 

Faraday has made the remarkable discovery, that if a very strong electric 
current is passed round a substance which possesses the property of circular 
polarization, the amount of rotation is altered to a considerable degree. 

The luminous rays of the sun are accompanied, as already mentioned, by 
others which possess heating powers. If the temperature of the different 
coloured spaces in the spectrum be tried with a delicate thermometer, it 
will be found to increase from the violet to the red extremity, and when the 
prism is of some particular kinds of glass, the greatest effect will be mani- 
fest a little beyond the visible red ray. It is inferred from this that the 
chief mass of the heating rays of the sun are among the least refrangible 
components of the solar beam. 

Again, it has long been known that chemical changes both of combination 
find of decomposition, but more particularly the latter, could be effected by 
the action of light. Chlorine and hydrogen combine at common tempera- 
tures only under the influence of light, and parallel cases occur in great 
numbers in organic chemistry : the blackening and decomposition of salts 
of silver are familiar instances of the chemical powers of the same agent. 
Now it is not the luminous part of the ray which effects these changes ; they 
are produced by certain invisible rays accompanying the others, and which 
are found most abundantly in and beyond the violet part of the spectrum. 
It is there that the chemical effects are most marked, although the intensity 
of the light is exceedingly feeble. The chemical rays are thus directly op- 
posed to the heating rays in the common spectrum in their degree of refran- 
gibility, since they exceed all the others in this respect. 

In the year 1802, 1 Mr. Thomas Wedgwood proposed a method of copying 
paintifegs on glass by placing behind them white paper or leather moistened 
with a solution of nitrate of silver, which became decomposed and blackened 
by the transmitted light in proportion to the intensity of the latter ; and 
Davy, in repeating these experiments, found that he could thus obtain tole- 
rably accurate representations of objects of a texture partly opaque and 
partly transparent, such as leaves and the wings of insects, and even copy 
with a certain degree of success the images of small objects obtained by the 
solar microscope. These pictures, however, required to be kept in the dark, 
and only examined by candle-light, otherwise they became obliterated by 
the blackening of the whole surface from which the salt of silver could not 
be removed. These attempts at light-painting attracted but little notice till 
the publication of Mr. Fox Talbot's' 2 papers, read before the Ptoyal Society, 
in January and February, 1839, in which he detailed two methods of fixing 
the pictures produced by the action of light on paper impregnated with 
chloride of silver, and at the same time described a plan by which the sen- 
sibility of the prepared paper may be increased to the extent required for 
receiving impressions from the images of the camera obscura. 

Very shortly afterwards, Sir John Herschel 3 proposed to employ solutions 
of the alkaline hyposulphites for removing the excess of chloride of silver 
from the paper, and thus preventing the farther action of light, and this 
plan has been found exceedingly successful. The greatest improvement, 
however, which the curious art of photogenic drawing has received, is due 
to Mr. Talbot, 4 who, in a communication to the Royal Society, described a 
method by which paper of such sensibility could be prepared as to permit 
its application to the taking of portraits of living persons by the aid of a 
good camera obscura, the time required for a perfect impression never ex- 
ceeding a few minutes. The portraits executed in this manner by Mr. 
Collen and others are beautiful in the highest degree, and leave little room 
for improvement in any respect. The process itself is rather complex, and 

* Journal of the Royal Institution, i. 170. 2 Phil. Map:. March, 1839 

» Phil. Trans, for 1S10, p. 1. * Phil. Mag. August, 1841, 

, 7* 



78 LIGHT. 

demands a great number of minute precautions, only to be learned by expe- 
rience, but which are indispensable to perfect success. The general plan is 
the following: — 

Writing-paper of good quality is washed on one side with a moderately 
dilute solution of nitrate of silver, and left to dry spontaneously in a dark 
room ; when dry, it is dipped into a solution of iodide of potassium, and 
again dried. These operations should be performed by candle-light. When 
required for use, the paper thus coated with yellow iodide of silver is brushed 
over with a solution containing nitrate of silver, acetic acid, and gallic acid, 
and once more carefully dried by gentle warmth. This kalotype paper is so 
sensitive, that exposure to diffused daylight for one second suffices to make 
an impression upon it, and even the light of the moon produces the ' same 
effect, although a much longer time is required. 

The images of the camera obscura are at first invisible, but are made to 
appear in full intensity by once more washing the paper with the above 
mentioned mixture, and warming it before the fire, when the blackening 
effect commences and reaches its maximum in a few minutes. 

The picture is of course negative, the lights and shadows being reversed ; 
to obtain positive copies nothing more is necessary than to place a piece of 
ordinary photographic paper prepared with chloride of silver beneath the 
kalotype impression, cover them with a glass plate, and expose the whole to 
the light of the sun for a short time. Before this can be done, the kalotype 
must however be fixed, otherwise it will blacken, and this is effected by im- 
mersion in a solution of hyposulphite of soda, and well washing with water. 

Sir John Herschel has shown that a great number of other substances can 
be employed in these photographic processes by talcing advantage of the 
singular deoxidizing effects of certain portions of the solar rays. Paper 
washed with a solution of a salt of sesquioxide of iron becomes capable of 
receiving impressions of this kind, which may afterwards be made evident 
by ferricyanide of potassium, or terchloride of gold. Vegetable colours are 
also acted upon in a very curious and apparently definite manner by the 
different parts of the spectrum. 1 

The Daguerreotype, the announcement of which was first made in the 
summer of 1839 by M. Daguerre, who had been occupied with this subject 
from 1826, if not earlier, is another remarkable instance of the decomposing 
effects of the solar rays. A clean and highly-polished plate of silvered 
copper is exposed for a certain period to the vapour of iodine, and then 
transported to the camera obscura. In the most improved state of the pro- 
cess, a very short time suffices for effecting the necessary change in the film 
of iodide of silver. The picture, however, only becomes visible by exposing 
it to the vapour of mercury, which attaches itself, in the form of exceed- 
ingly minute globules, to those parts which have been most acted upon, that 
is to say, to the lights, the shadows being formed by the dark polish of the 
metallic plate. Lastly, the drawing is washed with a solution of hyposul- 
phite of soda to remove the undecomposed iodide of silver, and render it 
permanent. 

The images of objects thus produced bear the most minute examination with 
a magnifying glass, the smallest details being depicted with perfect fidelity. 

Great improvements have been necessarily made in the application of this 
beautiful art to taking portraits. By the joint use of bromine and iodine 
the plates are rendered far more sensitive, and the time of sitting is short- 
ened to a very few seconds. When the operation is completed the colour of 
the plate is much improved by the deposition of an exceedingly thin film of 
gold, which communicates a warm purplish tint, and removes the previous 
dull leaden-grey hue, to most persons very offensive. 

1 Phil. Trans. 1S42, p. 1. 



RADIATION 1' HEAT. 79 



RADIATION, REFLECTION, ABSORPTION, AND TRANSMISSION 
OF HEAT. 

RADIATION OF HEAT. 

If a red-hot ball be placed upon a metallic support, and left to itself, 
cooling immediately commences, and only stops when the temperature of the 
ball is reduced to that of the surrounding air. This effect takes place in 
three ways : heat is conducted away from the ball through the substance of 
the support ; another portion is removed by the convective power of the air ; 
and the residue is thrown off from the heated body in straight lines or rays, 
which pass through air without interruption, and become absorbed by the 
surfaces of neighbouring objects which happen to be presented to their 
impact. 

This radiant or radiated heat resembles, in very many respects, ordinary 
light ; it suffers reflection from polished surfaces according to the same law ; 
it is absorbed by those that are dull or rough ; it moves with extreme velo- 
city ; and, finally, it traverses certain transparent media, undergoing refrac- 
tion at the same time, in obedience to the laws which regulate that pheno- 
menon in optics. 

The fact of the reflection of heat may be very easily proved. If a person 
stand before a fire in such a position that his face may be screened by the 
mantelshelf, and if he then take a bright piece of metal, as a sheet of tinned 
plate, and hold it in such a manner that the fire may be seen by reflection, 
at the same moment a distinct sensation of heat will be felt. 

The apparatus best fitted for studying these facts consists of a pair of con- 
cave metallic mirrors of the form called parabolic. The parabola is a curve 
possessing very peculiar properties, one of the most prominent being the 
following: — A tangent drawn to any part of the curve 
makes equal angles with two lines, one of which pro- Fi S- 54 - 

ceeds from the point where the tangent touches the 
curve in a direction parallel to what is called the axis 
of the parabola, and the other from the same spot 
through a point in front of the curve, called the focus. 
It results from this that parallel rays, either of light 
or heat, falling upon a mirror of this particular curva- 
ture in a direction parallel to the axis of the parabola, 
will be all reflected to a single point at the focus ; and 
rays diverging from this focus, and impinging upon the 
mirror, will, after reflection, become parallel (fig. 54). 

If two such mirrors be placed opposite to each other 
at a considerable distance, and so adjusted that their 
axes shall be coincident, and a hot body placed in the 
focus of the one, while a thermometer occupies that of the other, the reflec- 
tion of the rays of heat will become manifest by their effect upon the instru 
ment. In this manner, with a pair of by no means very perfect mirrors, 18 
inches in diameter, separated by an interval of 20 feet or more, amadou or 




so 



RADIATION OF HEAT, 



gunpowder may be readily fired by a red-hot ball in the focus of the oppo- 
site mirror (fig. 55). 

Fig. 55. 





The power of radiation varies exceedingly with different bodies, as may 
be easily proved. If two similar vessels of equal capacity be constructed 
of thin metal, and the surface of one highly polished, while that of the 
other is covered with lampblack, and both filled with hot w r ater of the same 
temperature, and their rate of cooling observed from time to time with a 
thermometer, it will be constantly found that the blackened vessel loses heat 
much faster than the one with bright surfaces ; and since both are put on a 
footing of equality in other respects, this difference, which will often amount 
to many degrees, must be ascribed to the superior emissive power of the film 
of soot. 

By another arrangement, a numerical comparison can be made of these 
differences. A cubical metallic vessel is prepared, each of whose sides is in 
a different condition, one being polished, another rough, a third covered 
with lampblack, &c. This vessel is filled with water, kept constantly at 
212° (100°C) by a small steam-pipe. Each of its sides is then presented in 
succession to a good parabolic mirror, having in its focus one of the bulbs 
of the differential thermometer before described (fig. 22), the bulb itself 
being blackened. The effect produced on this instrument is taken as a 
measure of the comparative radiating powers of the different surfaces. 
The late Sir John Leslie obtained by this method of experiment the follow- 
in £ results : — 



Emissive power. 

Lampblack 100 

Writing-paper 98 

Glass 90 

Plumbago 75 



Emissive power. 

Tarnished lead 45 

Clean lead 19 

Polished iron 15 

Polished silver 12 



The best reflecting surfaces are always the worst radiators ; polished 
metal reflects nearly all the heat that falls upon it, while its radiating power 
is the feeblest of any substance tried, and lampblack, which reflects nothing, 
radiates most perfectly. 

The power of absorbing heat is in direct proportion to the power of emis- 
sion. The polished metal mirror, in the experiment with the red-hot ball, 
remains quite cold, although only a few inches from the latter ; or, again, 
if a piece of gold leaf be laid upon paper, and a heated iron held over it 



1 The formerly supposed influence of mere difference of surface has been called in question 
liy M. Melloni, who attributes to other causes the effects observed by Sir John Leslie and 
others, among which superficial oxidation and difference of physical condition with respect 
to hardness and density, are among the most important. With metals not subject to tarnish, 
scratching the surface increases the emissive power when the plates have been rolled or 
hammered, i. e. are in a compressed state, and diminishes it. on the contrary, when the 
metal has been cast and carefully polished without burnishing. In the case of ivory, 
uvirble, and jet, where compression cannot take place, no diil'ereuce is perceptible in the 
vadiatiug pov,er of polished and rough surfaces. — Ann. Chim. et Phys. lxx. 435. 



RADIATION OF II E i-. T. 81 

until the paper is completely scorched, it will be found that the film of metal 
has perfectly defended that portion beneath it. 

The faculty of absorption seems to be a good deal influenced by colour; 
Dr. Franklin found that when pieces of cloth of various colours were placed 
on snow exposed to the feeble sunshine of winter, the snow beneath them 
became unequally melted, the effect being always in proportion to the depth 
of the colour; and Dr. Stark has since obtained a similar result by a dif- 
ferent method of experimenting. According to the late researches of Mel- 
loni, this effect depends less on the colour than on the nature of the colour- 
ing matter which covers the surface of the cloth. 

These facts afford an explanation of two very interesting and important 
natural phenomena, namely, the origin of dew, and the cause of the land 
and sea-breezes of tropical countries. While the sun remains above the 
horizon, the heat radiated by the surface of the earth into space is compen- 
sated by the absorption of the solar beams ; but when the sun sets, and this 
supply ceases, while the emission of heat goes on as actively as before, the 
surface becomes cooled until its temperature sinks below that of the air. 
The air in contact with the earth of course participates in this reduction of 
temperature ; the aqueous vapour present speedily reaches its point of max- 
imum density, and then begins to deposit moisture, whose quantity will de- 
pend upon the proportion of vapour in the atmosphere, and on the extent to 
which the cooling process has been carried. 

It is observed that dew is most abundant in a clear calm night, succeeding 
a hot day ; under these circumstances the quantity of vapour in the air is 
usually very great, and at the same time, radiation proceeds with most 
facility. At such times a thermometer laid on the ground will, after some 
time, indicate a temperature of 10° (5°-5C), 15° (8°-3C), or even 20° (11°-1C) 
below that of the air a few feet higher. Clouds hinder the formation of dew, 
by reflecting back to the earth the heat radiated from its surface, and thus 
preventing the necessary reduction of temperature : and the same effect is 
produced by a screen of the thinnest material stretched at a little height 
above the ground. In this manner gardeners often preserve delicate plants 
from destruction by the frosts of spring and autumn. The piercing cold felt 
just before and at sunrise, even in the height of summer, is the consequence 
of this refrigeration having reached its maximum. 

Wind also effectually prevents the deposition of dew, by constantly renew- 
ing the air lying upon the earth before it has had its temperature sufficiently 
reduced to cause condensation of moisture. 

Many curious experiments may be made by exposing on the ground at 
night, bodies which differ in their powers of radiation. If a piece of black 
cloth and a plate of bright metal be thus treated, the former will often be 
found in the morning covered with dew, while the latter remains dry. 

Land and sea-breezes are certain periodical winds common to most sea- 
coasts within the tropics, but by no means confined to those regions. It is 
observed, that a few hours after sunrise a breeze springs up at sea, and blows 
directly on shore, and that its intensity increases as the day advances, and 
declines and gradually expires near sunset. Shortly after, a wind arises in 
exactly the opposite direction, namely, from the land towards the sea, lasts 
the whole of the night, and only ceases with the reappearance of the sun. 

It is easy to give an explanation of these effects. When the sun shines 
at once upon the surface of the earth and that of the sea, the two become 
unequally heated from their different absorbing power : the land becomes 
much the warmer. The air over the heated surface of the ground, being ex- 
panded by heat, rises, and has its place supplied by colder air flowing from 
the sea, producing the sea-breeze. When the sun sets, both sea and land 
begin to cool by radiation; the rate of the cooling of the latter will, how- 



82 



TRANSMISSION OP HEAT, 



ever, far exceed that of the former, and its temperature "will rapidly fall. 
The air above becoming cooled and condensed, flows outwards in obedience 
to the laws of fluid pressure, and displaces the warmer air of the ocean. In 
this manner, by an interchange of air between sea and land, the otherwise 
oppressive heat is moderated, to the great advantage of those who inhabit 
such localities. The land and sea-breezes extend to a small distance only 
from shore, but afford, notwithstanding, essential aid to coasting navigation, 
since vessels on either tack enjoy a fair wind during the greater part of both 
day and night. 

TRANSMISSION OF HEAT; DIATHERMANCY. 

Rays of heat, in passing through air, receive no more obstruction than 
those of light under similar circumstances ; but with other transparent media 
the case is different. If a parabolic mirror be taken and its axis directed 
towards the sun, the rays both of heat and light will be reflected to the focus, 
which will exhibit a temperature sufficiently high to fuse a piece of metal, 
or fire a combustible body. If a plate of glass be now placed between the 
mirror and the sun, the effect will be but little diminished. 

Now, let the same experiment be made with the heat of a kettle filled with 
boiling water ; the heat will be concentrated by reflection as before, but, on 
interposing the glass, the heating effect at the focus will be reduced to 
nothing. Thus, the rays of heat coming from the sun traverse glass with 
facility, which is not the case with those emanating from the boiling water. 
In the year 1833, M. Melloni published the first of a series of exceedingly 
valuable researches on this subject, which are to be found in detail in various 
volumes of the Annales de Chemie et de Physique. 1 It will be necessary, in the 
first instance, to describe the method of operation followed by this philosopher. 
Not long before, two very remarkable facts had been 
discovered : Oersted, in Copenhagen, showed that a 
current of electricity, however produced, exercises a 
singular and perfectly definite action on a magnetic 
needle ; and Seebeck, in Berlin, found that an electric 
current may be generated by the unequal effects of heat 
on different metals in contact. If a wire conveying an 
electrical current be brought near a magnetic needle, 
the latter will immediately alter its position and assume 
a new one, as nearly perpendicular to the wire as the 
mode of suspension and the magnetism of the earth 
will permit. When the wire, for example, is placed 
directly over the needle (fig. 56), while the current it carries travels from 
north to south, the needle is deflected from its ordinary direction and the 
north pole driven to the eastward. When the current is reversed, the same 
pole deviates to an equal amount towards the west. Placing the wire below 
the needle instead of above produces the same effect as reversing the current. 
When the needle is subjected to the action of two currents in opposite 
directions, the one above and the other below, 
they will obviously concur in their effects. 
The same thing happens when the wire carry- 
ing the current is bent upon itself (fig. 57), 
and the needle placed between the two por- 
tions ; and since every time the bending is re- 
peated, a fresh portion of the current is made 
to act in the same manner upon the needle, it 
is easy to see how a current too feeble to pro- 
duce any effect when a simple straight wire is 



Pig. 56. 



Fig. 57. 




Translated also in Tayloi's Scientific Memoirs. 



TRANS M ISSION OF HEAT. 



83 



Fig. 58. 



employed, may be made by this contrivance to exhibit a powerful action on 
the magnet. It is on this principle that instruments called galvanometers, 
galvanoseopes, or multipliers, are constructed , they serve, not only to indicate 
the existence of electrical currents, but to show by the effect upon the needle 
the direction in which they are moving. By using a very long coil of wire, 
and two needles, immovably connected, and hung by a fine filament of silk, 
almost any degree of sensibility may be communicated to the apparatus. 

When two pieces of different metals, connected together at each end, have 
one of their joints more heated than the other, an electric current is imme- 
diately set up. Of all the metals tried, bismuth and antimony form the 
most powerful combination. A single pair of bars, having one of their junc- 
tions heated in the manner shown in fig. 58, can 
develop a current strong enough to deflect a 
compass-needle placed within, and, by ar- 
ranging a number in a series and heating their 
alternate ends, the intensity of the current may 
be very much increased. Such an arrangement 
is called a thermo-electric pile. M. Melloni 
constructed a thermo-electric pile of this kind, 
containing fifty-five slender bars of bismuth 
and antimony, laid side by side and soldered 
together at their alternate ends. He connected 
this pile with an exceedingly delicate multiplier, 
and found himself in the possession of an in- 
strument for measuring small variations of temperature far surpassing in 
delicacy the air-thermometer in its most sensitive form, and having gveat 
advantages in other respects over that instrument when employed for the 
purposes to which he devoted it. 

The substances whose powers of transmission were to be examined were 
cut into plates of a determinate thickness, and, after being well polished, 
arranged in succession in front of the little pile, the extremity of which was 
blackened to promote the absorption of the rays. (Fig. 59.) A perforated 




Fig. 59. 




screen, the area of whose aperture equalled that of the face of the pil<» 
was placed between the source of heat and the body under trial, while a 
second screen served to intercept all radiation until the moment of the ex- 
periment. 

After much preliminary labour for the purpose of testing the capabilities 
of the apparatus and the value of its indications, an extended series of re- 
searches was undertaken and carried on during a long period with great 
success : some of the most curious results are given in the subjoined table. 

Four different sources of heat were employed in these experiments, dif- 
fering in their degrees of intensity : the naked flame of an oil-lamp ; a coiJ 



84 



TRANSMISSION OF HEAT. 



of platinum wire heated to redness ; blackened copper at 734° (390°C) ; and 
the same heated to 212° (100°C). 



Substances. 
(Thickness of plate 0-1 inch, nearly.) 



Rock-salt, transparent and colourless. 

Fluor-spar, colourless 

Rock-salt, muddy 

Beryl 

Fluor-spar, greenish 

Iceland-spar 

Plate-glass 

Rock-crystal 

Rock-crystal, brown 

Tourmaline, dark green 

Citric acid, transparent 

Alum, transparent 

Sugar-candy 

Fluor-spar, green, translucent 

Ice, pure and transparent 



Transmission of 100 rays of 


heat from 


















ft 

a 




rto 




03 


TJ.9 


&e 


P^ 










© 




6* 


&h 








o* 


92 


92 


92 


92 


78 


69 


42 


33 


65 


65 


65 


65 


54 


23 


13 





46 


38 


24 


20 


39 


28 


6 





39 


24 


6 





38 


28 


6 





37 


28 


6 





.18 


16 


3 





11 


2 








9 


2 








8 











8 


6 


4 


3 


6 












On examining this remarkable table, "which is an abstract of one much 
more extensive, the first thing that strikes the eye is the want of connection 
between the power of transmitting heat and that of transmitting light ; 
taking, for instance, the oil-lamp as the source of heat, out of a quantity of 
heat represented by 100 rays falling upon the pile, the proportion intercepted 
by similar plates of rock-salt, glass, and alum, may be expressed by the 
numbers, 8, 61, and 91 ; and yet these bodies are equally transparent with 
respect to light. Generally speaking, colour was found to interfere with the 
transmissive power, but to a very unequal extent ; thus, in fluor-spar, coloui'- 
lcss, greenish, and deep-green, the quantities transmitted were 78, 46, and 
8, while the difference between colourless and brown rock-crystal was only 1. 
Bodies absolutely opaque, as wood, metals, and black marble, stopped the 
rays completely, although it was found that the faculty of transmission was 
possessed to a certain extent by some which were nearly in that condition, 
as thick plates of brown quartz, black mica, and black glass. 

When rays of heat had once passed through a plate of an}' substance, the 
interposition of a second similar plate occasioned much less loss than the 
first ; the same thing happened when a number were interposed ; the rays, 
after traversing one plate, being but little interrupted by others of a similar 
nature. 

The next point to be noticed is the grent difference in the propei'ties of 
'lie rays from different sources. Out of 100 rays from each source which 
fell on rock-salt, the same proportion was always transmitted, whether the 
rays proceeded from the intensely heated flame, the red-hot platinum wire, 
or the copper at 734° (390°C) or 212° (100°C) ; but this is true of no other 
substance in the list. In the case of plate-glass, we have the numbers 39, 
'24, 6, and 0, as representatives of the comparative quantities of heat trans 



TRANSMISSION OFH EAT. 85 

mitted through the plate from each source ; or in the three varieties of fluor- 
spar, as below stated : — 

Flame. Red-heat. 734° (390°C). 212° (100°C). 

Colourless 78 69 42 33 

Greenish 46 38 24 20 

Dark green 8 6 4 3 

While one substance, beryl, out of 100 rays from an intensely heated 
source, suffers 54 to pass, and from the same number (that is, an equal 
quantity of heat) from metal at 212° (100°C), none at all; another, fluor- 
spar, transmits rays from the two sources mentioned, in the proportion of 
8 to 3. 

These, and many other curious phenomena, are fully and completely 
explained on the supposition, that among the invisible rays of heat differ- 
ences are to be found exactly analogous to those differences between the 
rays of light which we are accustomed to call colours. Rock-salt and air are 
the only substances yet known which are truly diathermanous, or equally 
transparent to all kinds of heat-rays ; they are to the latter what white glass 
or water is to light ; they suffer rays of every description to pass with equal 
facility. All other bodies act like coloured glasses, absorbing certain of the 
rays more abundantly than the rest, and colouring, as it were, the heat which 
passes through them. 

These heat-tints have no direct relation to ordinary colours ; their exist- 
ence is, nevertheless, almost as clearly made out as that of the coloured 
rays of the spectrum. Bodies at a comparatively low temperature emit rays 
of such a tint only as to be transmissible by a few substances ; as the tem- 
perature rises, rays of other heat-colours begin to make their appearance, 
and transmission of some portion of these rays takes place through a greater 
number of bodies ; while at the temperature of intense ignition we find rays 
of all colours thrown out, some or other of which will certainly find their 
way through a great variety of substances. 

By cutting rock-salt into prisms and lenses, it is easy to show that radiant 
heat may be reflected like ordinary light, and its beams made to converge 
or diverge at pleasure ; and, lastly, to complete the analogy, it has been 
shown to be susceptible of polarization by transmission through plates of 
doubly-refracting minerals, in the same manner as light itself. 1 

1 Dr. Forbes, Phil. Mag. for 1S35 ; also M. Melloni, Ann. Chem. et Phys. lxv. 5. 



86 MAGNETISM. 



MAGNETISM. 

A particular species of iron ore has long been remarkable for its pro- 
perty of attracting small pieces of iron, and causing them to adhere to its 
surface : it is called loadstone, or magnetic iron ore. 

If a piece of this loadstone be carefully examined, it will be found that 
the attractive force for particles of iron is greatest at certain particular 
points of its surface, while elsewhere it is much diminished, or even alto- 
gether absent. These attractive points, or centres of greatest force, are 
denominated poles, and the loadstone itself is said to be endued with mag- 
netic polarity. 

If one of the poles of a natural loadstone be rubbed in a particular man- 
ner over a bar of steel, its characteristic properties will be communicated 
to the bar, which will then be found to attract iron-filings like the loadstone 
itself. Farther, the attractive force will be greatest at two points situated 
very near the extremities of the bar, and least of all towards the middle. 
The bar of steel so treated is said to be magnetised, or to constitute an arti- 
ficial magnet. 

When a magnetised bar or natural magnet is suspended at its centre in 
any convenient manner, so as to be free to move in a horizontal plane, it is 
always found to assume a particular direction with regard to the earth, one 
end pointing nearly north and the other nearly south. If the bar be moved 
from this position, it will tend to re-assume it, and, after a few oscillations, 
'Settle at rest as before. The pole which points towards the astronomical 
north is usually distinguished as the north pole of the bar, and that which 
points southward, as the south pole. A suspended magnet, either natural 
or artificial, of symmetrical form, serves to exhibit certain phenomena of 
attraction and repulsion in the presence of a second magnet, which deserve 
particular attention. When a north pole is presented to a south pole, or a 
south pole to a north, attraction ensues between them ; the ends of the bars 
approach each other, and, if permitted, adhere with considerable force ; 
when, on the other hand, a north pole is brought near a second north pole, 
or a south pole near another south pole, mutual repulsion is observed, and 
the ends of the bars recede from each other as far as possible. Poles of an 
opposite name attract, and of a similar name repel each other. Thus, a small 
bar or needle of steel, properly magnetized and suspended, and having its 
poles marked, becomes an instrument fitted not only to discover the exist- 
ence of magnetic power in other bodies, but to estimate the kind of polarity 
affected by their different parts. 

A piece of iron brought into the neighbourhood of a magnet acquires itself 
magnetic properties ; the intensity of the power thus conferred depends 
upon that of the magnet and upon the interval which divides the two ; be- 
coming greater as that interval decreases, and greatest of all when in actual 
contact. The iron under these circumstances is said to be magnetized by 
induction or influence, and the effect, which in an instant readies its maxi- 
mum, is at once destroyed by removing the magnet. 

When steel is substituted for iron in this experiment, the inductive action 
is hardly perceptible at first, and only becomes manifest after the lapse of a 
certain time ; iu this condition, when the steel bar is removed from the mag- 



MAGNETISM. 



87 



Fig. 60. 




■'■iiiill c 



3 




net, it retains a portion of the induced polarity. It becomes, indeed, a per- 
manent magnet, similar to the first, and retains its peculiar properties for 
an indefinite period. 

A particular name is given to this resistance which steel always offers in 
a greater or less degree both to the development of magnetism and its sub- 
sequent destruction; it is called specific coercive power. 

The rule which regulates the induction of magnetic polarity in all cases 
is exceedingly simple, and most important to be remembered. The pole pro- 
duced is always of the opposite name 
to that which produced it, a north pole 
developing south polarity, and a south 
pole north polarity. The north pole of 
the magnet, shown in fig, 60, induces 
south polarity in all the nearer extre- 
mities of the pieces of iron or steel 
which surround it, and a state similar 
to its own in all the more remote extre- 
mities. The iron thus magnetized is 
capable of exerting a similar inductive 
action on a second piece, and that upon 
a third, and so to a great number, the 
intensity of the force diminishing as 
the distance from the permanent mag- 
net increases. It is in this way that a 
magnet is enabled to hold up a number 
of small pieces of iron, or a bunch of 
filings, each separate piece becoming a 
magnet for the time by induction. 

Magnetic polarity, similar to that which iron presents, has been found 
only in some of the compounds of iron, in nickel, and in cobalt. 

Magnetic attractions and repulsions are not in the slightest degree inter- 
fered with by the interposition of substances destitute of magnetic proper- 
ties. Thick plates of glass, shellac, metals, wood, or of any substances 
except those above mentioned, may be placed between a magnet and a sus- 
pended needle, or a piece of iron under its influence, the distance being pre- 
served, without the least perceptible alteration in its attractive power, or 
force of induction. 

One kind of polarity cannot be exhibited without the other. In other 
words, a magnetic pole cannot be insulated. If a magnetized bar of steel 
be broken at its neutral point, or in the middle, each of the broken ends ac- 
quires an opposite pole, so that both portions of the bar become perfect 
magnets ; and, if the division be carried still farther, if the bar be broken 
into a hundred pieces, each fragment will be a complete magnet, having its 
own north and south poles. 

This experiment serves to show very clearly that the apparent polarity of 
the bar is the consequence of the polarity of each individual particle, the 
poles of the bar being merely points through which the resultants of all 
these forces pass ; the large magnet is made up of an immense number of 
little magnets regularly arranged side by side (fig. 61), all having their north 

Fig. 61. 




88 MAGNETISM. 

poles looking one way, and their south poles the other. The middle portion 
of such a system cannot possibly exhibit attractive or repulsive effects on an 
external body, because each pole is in close juxta-position with one of an 
opposite name and of equal power ; hence their forces will be exerted in op- 
posite directions and neutralize each other's influence. Such will not be the 
case at the extremities of the bar ; there uncompensated polarity will be 
found capable of exerting its specific power. 

This idea of regular polarization of particles of matter in virtue of a pair 
of opposite and equal forces, is not confined to magnetic phenomena ; it is 
the leading principle in electrical science, and is constantly reproduced in 
some form or other in every discussion involving the consideration of mole- 
cular forces. 

Artificial steel magnets are made in a great variety of forms ; such as 
small light needles, mounted with an agate cap for suspension upon a fine 
point ; straight bars of various kinds ; bars curved into the shape of a horse- 
shoe, &c. All these have regular polarity communicated to them by cer- 
tain processes of rubbing or touching with another magnet, which require 
care, but are not otherwise difficult of execution. When great power is 
wished for, a number of bars may be screwed together, with their similar 
ends in contact, and in this way it is easy to construct permanent steel mag- 
nets capable of sustaining great weights. To prevent the gradual destruc- 
tion of magnetic force, which would otherwise occur, it is usual to arm each 
pole with a piece of soft iron or keeper, which, becoming magnetized by in- 
duction, serves to sustain the polarity of the bar, and even increases in some 
cases its energy. 

The direction spontaneously assumed by a suspended needle indicates that 
the earth itself has the properties of an enormous magnet, whose south pole 
is in the northern hemisphere. A line joining the two poles of such a 
needle or bar indicates the direction of the magnetic meridian of the place, 
which is a vertical plane coincident with the direction of the needle. 

The magnetic meridian of a place is not usually coincident with its geo- 
graphical meridian, but makes with the latter a certain angle called the de- 
clination of the needle ; in other words, the magnetic poles are not situated 
within the line of the axis of rotation. 

The amount of this declination of the needle from the true north and 
south not only varies at different places, but in the same place is subject to 
daily, yearly, and secular fluctuations, which are called the variations of 
declination. Thus, at the commencement of the 17th century, the declina- 
tion was eastward; in 1660, it was 0; that is, the needle pointed due north 
and south. Afterwards it became westerly, slowly increasing until the year 
1818, when it reached 24° S0 / , since which time it has been slowly di- 
minishing. 

If a steel bar be supported on a horizontal axis passing exactly through 
its centre of gravity, it will of course remain equally balanced in any posi- 
tion in which it may happen to be placed ; if the bar so adjusted be then 
magnetized, it will be found to take a permanent direction, the north pole 
being downwards, and the bar making an angle of about 70°, with a hori- 
zontal plane passing through the axis. This is called the dip, or inclination 
of the needle, and shows the direction in which the force of terrestrial mag- 
netism is most energetically exerted. The amount of this dip is different in 
different latitudes ; near the equator it is very small, the needle remaining 
nearly or quite hox-izontal ; as the latitude increases the dip becomes more 
decided ; and over the magnetic pole the bar becomes completely vertical. 
Such a situation is in fact to be found in the northern hemisphere, consider- 
ably to the westward of the geographical pole, in Prince Regent's Inlet. 
lat. 70° 5 / N. and longitude 96° 46 / W. ; the dipping-needle has here been 



MAGNETISM. 89 

seen to point directly downwards, while the horizontal or compass-needle 
ceased to traverse. The position of the south magnetic pole has lately been 
determined, by the observations of Captain Ross, to be about lat. 73° S. and 
long. 130° E. 

By observing a great number of points near the equator in which the dip 
becomes reduced to nothing, a line may be traced around the earth, called 
the magnetic equator, and nearly parallel to this, on both sides, a number 
of smaller circles, called lines of equal dip. These lines present great irreg- 
ularities when compared with the equator itself and the parallels of lati- 
tude, the magnetic equator deviating from the terrestrial one as much as 12° 
at its point of greatest divergence. Like the horizontal declination, the dip 
is also subject to change at the same place. Observations have not yet been 
made during sufficient time to determine accurately the law and rate of alte- 
ration, and great practical difficulties exist also in the construction of the 
instruments. In the year 1773 it was about 72° ; at the present time it is 
near 69° 5 / in London. 

The inductive power of the magnetism of the earth may be shown by 
holding in a vertical position a bar of very soft iron ; the lower end will be 
found to possess north polarity, and the upper, the contrary state. On re- 
versing the bar the poles are also reversed. All masses of iron whatever, 
when examined by a suspended needle, will be found in a state of magnetic 
polarity by the influence of the earth ; iron columns, tools in a smith's shop, 
tire-irons, and other like objects, are all usually magnetic, and those made 
of steel permanently so. On board ship, the presence of so many large 
masses of iron, guns, anchors, water-tanks, &c, thus polarized by the earth, 
causes a derangement of the compass-needles to a very dangerous extent ; 
happily, a plan has been devised for determining the amount of this local 
attraction in different positions of the ship, and making suitable corrections. 

The mariner's compass, which is nothing more than a suspended needle 
attached to a circular card marked with the points, was not in general use 
in Europe before the year 1300, although the Chinese have had it from very 
early antiquity. Its value to the navigator is now very much increased by 
correct observations of the exact amount of the declination in various parts 
of the world. 

Probably every substance in the world contributes something to the mag- 
netic action of the earth ; for, according to the latest discoveries of Mr. 
Faraday, magnetism is not peculiar to those substances which have more 
especially been called magnetic, such as iron, nickel, cobalt, but it is the 
property of all matter, though to a much smaller degree. Very powerful 
magnets are required to show this remarkable fact. Large horse-shoe mag- 
nets, made by the action of the electric current, are most proper. The 
magnetic action on different substances which are capable of being easily 
moved, differs not only according to the size, but also according to the nature 
of the substance. In consequence of this, Faraday divides all bodies into 
two classes. He calls the one magnetic, or, better, paramagnetic, and the 
other diamagnetic. 

The matter of which a paramagnetic (magnetic) body consists is attracted 
by both poles of the horse-shoe magnet; on the contrary, the matter of a 
diamagnetic body is repelled. "When a small iron bar is hung by untwisted 
silk between the poles of the magnet, so that its long diameter can easily 
move in a horizontal plane, it arranges itself axially, that is, parallel to the 
straight line which joins the poles, or to the magnetic axis of the poles ; 
assuming at the end which is nearest the north pole, a south pole, and at 
the end nearest the south pole, a north pole. Whenever the little bar is 
removed from this position, after a few oscillations, it returns again to its 
previous position. The whole class of paramagnetic bodies behave in a pre- 



90 MAGNETISM. 

eisely similar way under similar circumstances ; only in the intensity of the 
effects great differences occur. 

On the contrary, diamagnetic bodies have their long diameters placed 
equatorially, that is, at right angles to the magnetic axis. They behave, as 
if at the end opposite to each pole of the magnet, the same kind of polarity 
existed. 

In the first class of substances, besides iron, which is the best representa- 
tive of the class, -we have nickel, cobalt, manganese, chromium, cerium, 
titanium, palladium, platinum, osmium, aluminium, oxygen, and also most 
of the compounds of these bodies ; most of them, even when in solution. 
According to Faraday, the following substances are also feebly paramagnetic 
(magnetic) ; paper, sealing-wax, indian-ink, porcelain, asbestos, fluor-spar, 
minium, cinnabar, binoxide of lead, sulphate of zinc, tourmaline, graphite, 
and charcoal. 

In the second class are placed bismuth, antimony, zinc, tin, cadmium, 
sodium, mercury, lead, silver, copper, gold, arsenic, uranium, rhodium, 
iridium, tungsten, phosphorus, iodine, sulphur, chlorine, hydrogen, and many 
of their compounds. Also, glass free from iron, water, alcohol, ether, nitric 
acid, hydrochloric acid, resin, wax, olive oil, oil of turpentine, caoutchouc, 
sugar, starch, gum, and wood. These are diamagnetic. 

If diamagnetic and paramagnetic bodies are combined, their peculiar pro- 
perties are destroyed. In most of these compounds, occasionally, in conse- 
quence of the presence of the smallest quantity of iron, the peculiar mag- 
netic power remains more or less in excess. Thus green bottle glass and many 
varieties of crown glass are magnetic in consequence of the iron in them. 

In order to examine the magnetic properties of fluids they are placed in 
very thin glass tubes, the ends of which are closed by melting, they 
are then hung horizontally between the poles of the magnet. Under the 
influence of poles sufficiently powerful, they begin to swing, and accord- 
ing as the fluid contents are paramagnetic (magnetic), or diamagnetic, they 
assume an axial or equatorial position. 

Under certain circumstances substances which belong to the paramagnetic 
class behave as if they were diamagnetic. This happens in consequence of 
a differential action. Thus, for example, when a glass tube full of a dilute 
solution of sulphate of iron is allowed to swing in a concentrated solution 
of sulphate of iron, instead of in the air, it assumes an equatorial position. 
The air, in consequence of the oxygen in it, is itself paramagnetic (magnetic). 
Hence such bodies as appear to possess feeble diamagnetic properties, can 
only show their true properties when hung in a vacuum. 

Faraday has tried the magnetic condition of gases in different ways. One 
way consisted in making soap bubbles with the gas which he wished to in- 
vestigate, and bringing these near the poles. Soap and water alone is feebly 
diamagnetic. A bubble filled with oxygen was strongly attracted by the 
magnet. All other gases in the air are diamagnetic, that is, they are re- 
pelled. But, as Faraday has shown, in a different way, this partly arises 
from the paramagnetic (magnetic) property of the air. Thus he found that 
nitrogen, when this differential action was eliminated, was perfectly indif- 
ferent, whether it was condensed or rarified, whether cooled or heated. 
When the temperature is raised, the diamagnetic property of gases in the 
air is increased. Hence the flame of a candle or of hydrogen is strongly 
repelled by the magnet. Even warm air is diamagnetic in cold air. 

For some time it has been believed that bodies in a crystalline form had a 
special and peculiar behaviour when placed between the poles of a magnet. 
It appeared as though the magnetic directing power of the crystal had some 
peculiar relation to the position of its optic axis ; so that, independently of 
the magnetic property of the substance of the crystal, if the crystal was 



MAGNETISM. 91 

positively optical, it possessed the power of placing its optic axis parallel 
with the line which joined the poles of the magnet, while optically negative 
crystals tried to arrange their axes at right angles to this line. This suppo- 
sition is disproved by the excellent investigation of Knoblauch and Tyndall. 
It follows from their observations that the peculiarity in regard to crystals 
is dependent on their internal state of cohesion, that is, on unequal com- 
pression in different directions. If crystalline, or even uncrystalline sub- 
stances are unequally compressed in different directions, they are found to 
possess a preponderating directive force in the direction in which they are 
most strongly compressed, so that when this direction does not coincide with 
the long diameter of the body, magnetic bodies will even arrange themselves 
equatorially, and diamagnetic bodies axially. 



<J2 ELECTRICITY. 



ELECTRICITY. 

If glass, amber, or sealing-wax, be rubbed with a dry cloth, it acquires the 
power of attracting light bodies, as feathers, dust, or bits of paper; this is 
the result of a new and peculiar condition of the body rubbed, called elec- 
trical excitation. 

If a light downy feather be suspended by a thread of white silk, and a 
dry glass tube, excited by rubbing, be presented to it, the feather will be 
strongly attracted to the tube, adhere to its surface for a few seconds, and 
then fall off. If the tube be now excited anew, and presented to the feather, 
the latter will be strongly repelled. 

The same experiment may be repeated with shellac or resin ; the feather 
in its ordinary state will be drawn towards the excited body, and after 
touching, again driven from it with a certain degree of force. 

Now, let the feather be brought into contact with the excited glass, so as 
to be repelled by that substance, and let a piece of excited sealing-wax be 
presented to it ; a degree of attraction will be observed far exceeding that 
exhibited when the feather is in its ordinary state. Or, again, let the feather 
be made repulsive for sealing-wax, and then the excited glass be presented ; 
strong attraction will ensue. 

The reader will at once see the perfect parallelism between the effects 
described and some of the phenomena of magnetism ; the electrical excite- 
ment having a twofold nature, like the opposite polarities of the magnet. 
A body to which one kind of excitement has been communicated is attracted 
by another body in the opposite state, and repelled b}' one in the same state. 
The excited glass and resin being to each other as the north and south poles 
of a pair of magnetized bars. 

To distinguish these two different forms of excitement, terms are em- 
ployed, which, although originating in some measure in theoretical views of 
the nature of the electrical disturbance, may be understood by the student 
as purely arbitrary and distinctive ; it is customary to call the electricity 
manifested by glass positive or vitreous, and that developed in the case of 
shellac, and bodies of the same class, negative or resinous. The kind of elec- 
tricity depends in some measure upon the nature of the surface ; smooth 
glass rubbed with silk or wool becomes ordinarily positive, but when ground 
or roughened by sand or emery, it acquires, under the same circumstances, 
a negative charge. 

The repulsion shown by bodies in the same electrical state is taken advan- 
tage of to construct instruments for indicating electrical excitement and 
pointing out its kind. Two balls of alder-pith (fig. 02), hung by threads or 
very fine metal wires, serve this purpose in many cases ; they open out when 
excited, in virtue of their mutual repulsion, and show by the degree of diver- 
gence the extent to which the excitement has been carried. A pair of gold 
leaves suspended beneath a bell jar, and communicating with a metal cap 
above (fig. 63), constitute a much more delicate arrangement, and one of 
great value in all electi'ical investigations. These instruments are called 
electroscopes or electrometers; when excited by the communication of a 
known kind of electricity, they show, by an increased or diminished diver- 
gence, the state of an electrified body brought into their neighbourhood. 



ELECTRICITY. 



93 



Fig. 62. 



Fig. 63. 





One kind of electricity can no more be developed -without the other than 
one kind of magnetism ; the rubber and the body rubbed always assume 
opposite states, and the positive condition on the surface of a mass of matter 
is invariably accompanied by a negative state in all surrounding bodies. 

The induction of magnetism in soft iron has its exact counterpart in elec- 
tricity ; a body already electrified disturbs or polarizes the particles of all 
surrounding substances in the same manner and according to the same law, 
inducing a state opposite to its own in the nearer portions, and a similar 
state in the more remote parts. A series of globes suspended by silk threads, 
in the manner represented in fig. 64, will each become electric by induction 

Fig. 64. 



when a charged body is brought near the end of the series, like so many 
pieces of iron in the vicinity of a magnet, the positive half of each globe 
looking in one and the same direction, and the negative half in the opposite 
one. The positive and negative signs are intended to represent the states. 

The intensity of the induced electrical disturbance diminishes with the 
distance from the charged body ; if this be removed or discharged, all the 
effects cease at once. 

So far, the greatest resemblance may be traced between these two sets of 
phenomena ; but here it seems in great measure to cease. The magnetic 
polarity of a piece of steel can awaken polarity in a second piece in contact 
with it by the act of induction, and in so doing loses nothing whatever of 
its power ; this is an effect completely different from the apparent transfer 
or discbarge of electricity constantly witnessed, which in the air and in 
liquids often give rise to the appearance of a bright spark of fire. Indeed, 
ordinary magnetic effects comprise two groups of phenomena only, those 
namely of attraction and repulsion, and those of induction. But in elec- 
tricity, in addition to phenomena very closely resembling these, we have the 
effects of discharge, to which there is nothing analogous in magnetism, and 
which takes place in an instant when any electrified body is put in commu 



94 ELECTRICITY. 

nication -with the earth by any one of the class of substances called con- 
ductors of electricity ; all signs of electrical disturbance then ceasing. 

These conductors of electricity, which thus permit discharge to take place 
through their mass, are contrasted with another class of substances called 
non-conductors or insulators. The difference, however, is only one of degree, 
not of kind ; the very best conductors offer a certain resistance to the elec- 
trical discharge, and the most perfect insulators permit it to a small extent. 
The metals are by far the best conductors ; glass, silk, shellac, and dry gas, 
or vapour of any sort, the very worst ; and between these there are bodies 
of all degrees of conducting power. 

Electrical discharges take place silently and without disturbance in good 
conductors of sufficient size. But if the charge be very intense, and the 
conductor very small or imperfect from its nature, it is often destroyed with 
violence. 

When a break is made in a conductor employed in effecting the discharge 
of a highly-excited body, disruptive or spark-discharge, so well known, takes 
place across the intervening air, provided the ends of the conductor be not 
too distant. The electrical spark itself presents many points of interest in 
the modifications to which it is liable. 

The time of transit of the electrical wave through a chain of good conduct- 
ing bodies of great length is so minute as to be altogether inappreciable to 
ordinary means of observation. Professor Wheatstone's very ingenious ex- 
periments on the subject give, in the instance of motion through a copper 
wire, a velocity approaching that of light. 

Electrical excitation is apparent only upon the surfaces of bodies, or those 
portions directed towards other objects capable of assuming the opposite 
state. An insulated ball charged with positive electricity, and placed in the 
centre of the room, is maintained in that state by the inductive action of the 
walls of the apartment, which immediately become negatively electrified ; in 
the interior of the ball there is absolutely no electricity to be found, although 
it may be constructed of open metal gauze, with meshes half an inch wide. 
Even on the surface the distribution of electrical force will not always be the 
same ; it will depend upon the figure of the body itself, and its position with 
regard to surrounding objects. The polarity will always be highest in the 
projecting extremities of the same conducting mass, and greatest of all when 
these are attenuated to points, in which case the inequality becomes so great 
that discharge takes place to the air, and the excited condition cannot be 
maintained. 

The construction and use of the common electrical machine, and other 
pieces of apparatus of great practical utility, will, by the aid of these prin- 
ciples, become intelligible. 

A glass cylinder (fig. 65) is mounted with its axis in a horizontal position, 
and provided with a handle or winch by which it may be turned. A leather 
cushion is made to press by a spring against one side of the cylinder, while 
a large metal conducting body, armed with a number of points next the 
glass, occupies the other; both cushion and conductor are insulated by glass 
supports, and to the upper edge of the former a piece of silk is attached 
long enough to reach half round the cylinder. Upon the cushion is spread 
a quantity of a soft amalgam of tin, zinc, and mercury, 1 mixed up with a 
little grease ; this substance is found by experience to excite glass most 
powerfully. The cylinder, as it turns, thus becomes charged by friction 
against the rubber, and as quickly dischai-ged by the row of points attached 
to the great conductor ; and as the latter is also completely insulated, its 
surface speedily acquires a charge of positive electricity, which may be 

1 Part tin, 2 zinc, and 6 mercury. 



ELECTRICITY. 

Fig. 65. 



95 




communicated by contact to other insulated bodies. The maximum effect is 
produced when the rubber is connected by a chain or wire with the earth. 
If negative electricity be wanted, the rubber must be insulated and the con- 
ductor discharged. 

Another form of the electrical machine consists of a circular plate of glass 
(fig. 66) moving upon an axis, and provided with two pairs of cushions or 

Fig. 66. 




96 



ELECTRICITY 



or rubbers, attached to the upper and lower parts of the wooden frame, 
covered with amalgam, between which the plate moves with considerable 
friction. An insulated conductor, armed as before with points, discharges 
the plate as it turns, the rubbers being at the same time connected with the 
ground by the wood-work of the machine, or by a strip of metal. Thi3 
modification of the apparatus is preferred in all cases where considerable 
power is wanted. 

In the practical management of electrical apparatus, great care must be 
taken to prevent deposition of moisture from the air upon the surface of the 
glass supports, which should always be varnished with fine lac dissolved in 
alcohol ; the slightest film of water is sufficient to destroy the power of insu- 
lation. The rubbers also must be carefully dried before use, and the amal- 
gam renewed if needful ; in damp weather much trouble is often experienced 
in bringing the machine into powerful action. 

When the conductor of the machine is charged with electricity, it acts 
indirectly on, and accumulates the contrary electricity to its own, at the sur- 
face of all the surrounding conductors. It produces the greatest effect on 
the conductor that is nearest to it, and which is in the best connection with 
the ground, whereby the electricity of the same kind as that of the machine 
may pass to the earth. As the inducing electricity attracts the induced 
electricity of an opposite kind ; so, on the other hand, is the former attracted 
by the latter. Hence the fluid which the conductor receives from the ma- 
chine must especially accumulate at that spot to which another good con- 
ductor of electricity is opposed. If a metal disc is in connection with the 
conductor of a machine, and if another similar disc, which is in good con- 
nection with the earth, is placed opposite to it, we have an arrangement by 
which tolerably large and good conducting surfaces can be brought close to 
one another; thus the positive condition of the first disc, as well as the nega- 
tive condition of the other, must be increased to a very considerable degree ; 
the limit is in this case, however, soon reached, because the intervening air 
easily permits spark-discharge to take place through its substance. With a 
solid insulating body, as glass or lac, this happens with 
much greater difficulty, even when the plate of insulating 
matter is very thin. It is on this principle that instru- 
ments for the accumulation of electricity depend, among 
which the Ley den jar is the most important. 

A thin glass jar (fig. 67) is coated on both sides with tin- 
foil, care being taken to leave several inches of the upper 
part uncovered ; a wire, terminating in a metallic knob, 
communicates with the internal coating ; when the outside 
of the jar is connected with the earth, and the knob put 
in contact with the conductor of the machine, the inner 
and outer surfaces of the glass become respectively posi- 
tive and negative, until a very great degree of intensity 
has been attained. On completing the connection between 
the two coatings by a metallic wire or rod, discharge oc- 
curs in the form of an exceedingly bright spark, accom- 
panied by a loud snap ; and if the body be interposed in the circuit, the 
peculiar and disagreeable sensation of the electric shock is felt at the mo- 
ment of its completion. 

By enlarging the dimensions of the jar, or by connecting together a number 
in such a manner that all may be charged and discharged simultaneously, 
the power of the apparatus may be greatly augmented. Thin wires of metal 
may be fused and dissipated ; pieces of wood may be shattered, many com- 
bustible substances set on fire, and all the well-known effects of lightning 
exhibited upon a small scale. 



Pig. 67. 





ELECTRICITY. 97 

The electric spark is often very conveniently employed in chemical inqui- 
ries for firing gaseous mixtures in close vessels. A small Leyden jar charged 
by the machine is the most effective contrivance for this purpose, but, not 
unfrequently, a method may be resorted to which involves less preparation. 
This is by the use of the electrophorus. 

A round tray or dish of tinned plate is Fi S- 68 » 

prepared (fig. 68), having a stout wire 
round its upper edge ; the width may be 
about twelve inches, and the depth half 
an inch. This tray is filled with melted 
shellac, and the surface rendered as even 
as possible. A brass disc, with rounded 
edge, of about nine inches diameter, is 
also provided, and fitted with an insulating 
handle. When a spark is wanted, the 
resinous plate is excited by striking with 

a dry, warm piece of fur, or a silk handkerchief; the cover is placed upon 
it, and touched by the finger. When the cover is raised, it is found so 
strongly charged by induction with positive electricity, as to give a bright 
spark ; and, as the resin is not discharged by the cover, which merely 
touches it at a few points, sparks may be drawn as often as may be wished. 

It is not known to what cause the disturbance of the electrical equilibrium 
of the atmosphere is due ; experiment has shown that the higher regions of 
the air are usually in a positive state, the intensity of which reaches a maxi- 
mum at a particular period of the day. In cloudy and stormy weather the 
distribution of the atmospheric electricity becomes much deranged, clouds 
near the surface of the earth often appearing in a negative state. 

The circumstances of a thunder-storm exactly resemble those of the 
charge and discharge of a coated plate or jar ; the cloud and the earth repre- 
sent the two coatings, and the intervening air the bad-conducting body or 
dielectric. The polarities of the opposed surface and of the insulating medium 
between them become raised by mutual induction, until violent disruptive 
discharge takes place through the air itself, or through any other bodies 
which may happen to be in the interval. When these are capable of con- 
ducting freely, the discharge is silent and harmless ; but in other cases it 
often proves highly destructive. These dangerous effects are now in a great 
measure obviated by the use of lightning-rods attached to buildings, the 
erection of which, however, demands a number of precautions not always 
Tindevstood or attended to. The masts of ships may be guarded in like 
manner by metal conductors ; Sir W. Snow Harris has devised a most inge- 
nious plan for the purpose, which is now adopted, with the most complete 
success, in the British Navy. 

When two solid conducting bodies are plunged into a liquid which acts 
upon them unequally, the electric equilibrium is also disturbed, the one ac- 
quiring the positive condition, and the other the negative. Thus, pieces of 
zino and platinum put into dilute sulphuric acid, constitute an arrangement 
capable of generating electrical force ; the zinc being the metal attacked, 
becomes negative; and the platinum remaining unaltered, assumes the posi- 
tive condition ; and on making a metallic communication in any way between 
the two plates, discharge ensues, as when the two surfaces of a coated and 
charged jar are put into connection. 

No sooner, however, has this occurred, than the disturbance is repeated, 
and as these successive charges and discharges take place through the fluid 
and metals with inconceivable rapidity, the result is an apparently continuous 
action, to which the term electrical current is given. 

It is necessary to guard against the idea which the term naturally suggests, 
9 



98 



ELECTRICITY. 



Fig. 69. 



of an actual bodily transfer of something through the substance of the con- 
ductors, like water through a pipe ; the real nature of all these phenomena 
is entirely unknown, and may perhaps remain so ; the expression is conve- 
nient notwithstanding, and consecrated by long use ; and with this caution, 
the very dangerous error of applying figurative language to describe an 
effect, and then seeking the nature of the effect from the common meaning 
of words, may be avoided. 

The intensity of the electrical excitement developed by a single pair of 
metals and a liquid, is too feeble to affect the most delicate gold-leaf elec- 
troscope ; but, by arranging a number of such alternations 
in a connected series, in such a manner, that the direction 
of the current shall be the same in each, the intensity 
may be very greatly exalted. The two instruments in- 
vented by Volta, called the pile, and crown of cups, depend 
upon this principle. 

Upon a plate of zinc (fig. 69) is laid a piece of cloth, 
rather smaller than itself, steeped in dilute acid, or any 
liquid capable of exerting chemical action upon the zinc ; 
upon this is placed a plate of copper, silver, or platinum ; 
then a second piece of zinc, another cloth, and plate of 
inactive metal, until a pile of about twenty alternations 
has been built up. If the two terminal plates be now 
touched with wet hands, the sensation of the electric 
shock will be experienced; but, unlike the momentary 
effect produced by the discharge of a jar, the sensation 
will be prolonged and continuous, and with a pile of one hundred such pairs, 
excited by dilute acid, it will be nearly insupportable. When such a pile is 
insulated, the two extremities exhibit strong positive and negative states, and 
when connection is made between them by wires armed with points of hard 
charcoal or plumbago, the discharge takes place in the form of a bright en- 
during spark or stream of fire. 

The second form of apparatus, or crown of cups, is precisely the same in 
principle, although different in appearance. A number of cups or glasses 




^g- 



"0) are arranged in a row or circle, each containing a piece of active and 
Ffe. 70. 




piece of inactive metal, and a portion of exciting liquid; zinc, copper, and 
dilute sulphuric acid, for example. The copper of the first cup is connected 
with the zinc of the second, the copper of the second with the zinc of the 
third, and so to the end of the series. On establishing a communication 
between the first and last plates by means of a wire, or otherwise, discharge 
takes place as before. 

When any such electrical arrangement consists merely of a single pair of 
conductors and an interposed liquid, it is called a simple circuit; when _ two 
OT more alternations are concerned, the term " compound circuit" i* Applied ; 
they are called also, indifferently, voltaic batteries. In every fevi» of such 



ELECTRICITY. 



99 



apparatus, however complex it may appear, the direction of the current may 
be easily understood and remembered. The polarity or disturbance may be 
considered to commence at the surface of the metal attacked, and to be pro- 
pagated through the liquid to the inactive conductor, and thence back again 
by the connecting wire, these extremities of the battery being always re- 
spectively negative and positive when the apparatus is insulated. In common 
parlance, it is said that the current in every battery in an active state starts 
from the metal attacked, passes through the liquid to the second metal or 
conducting body, and returns by the wire or other channel of communica- 
tion; hence, in the pile and crown of cups just described, the current in the 
battery is always from the zinc to the copper ; and out of the battery, from 
the copper to the zinc, as shown by the arrows. 

In the modification of Volta's original pile, made by Mr. Cruikshank, the 
zinc and copper plates are soldered together and cemented water-tight into 
a mahogany trough (fig. 71), which thus becomes divided into a series of 

Fig. 71. 




cells or compartments capable of receiving the exciting liquid. This appa- 
ratus is well fitted to exhibit effects of tension, to act upon the electroscope 
and give shocks ; hence its advantageous employment in the application of 
electricity to medicine, as a very few minutes suffices to prepare it for use. 
The crown of cups was also put into a much more manageable form by Dr. 
Babington, and still farther improved, as will hereafter be seen, by Dr. 
Wollaston. Subsequently, various alterations have been made by different 
experimenters with a view of obviating certain defects in the common bat- 
teries, of which a description will be found towards the middle of this 
volume. 

The term "galvanism," sometimes applied to this branch of electrical 
science, is used in honour of Professor Galvani, of Bologna, who, in 1790, 
made the very curious observation that convulsions could be produced in the 
limbs of a dead frog when certain metals were made to touch the nerve and 
muscle at the same moment. It was Volta, however, who pointed out the 
electrical origin of these motions, and although the explanation he offered 
of the source of the electrical disturbance is no longer generally adopted, 
his name is very properly associated with the invaluable instrument his 
genius gave to science. 

In the year 1822, Professor Seebeck, of Berlin, discovered another source 
of electricity, to which allusion has already been made, namely, inequality 
of temperature and conducting power in different metals placed in contact, 
or in the same metal in different states of compression and density. Even 
with a great number of alternations, the current produced is exceedingly 
feeble compared with that generated by the voltaic pile. 

Two or three animals of the class of fishes, as the torpedo, or electric ray, 
and the electric eel of South America, are furnished with a special organ or 
apparatus for developing electrical force, which is employed in defence, or 
in the pursuit of prey. Electricity is here seen to be closely connected with 
nervous power ; the shock is given at the will of the animal, and great ex- 
haustion follows repeated exertion of the power. 

Although the fact that electricity is capable, under certain circumstances, 
fcoth of inducing and of destroying magnetism, has long been known, from 



100 ELECTRICITY. 

the effects of lightning on the compass-needle and upon small steel articles, 
as knives and forks, to which polarity has suddenly been given by the stroke, 
it was not until 1819 that the laws of these phenomena were discovered by 
Professor (Ersted, of Copenhagen, and shortly afterwards fully developed by 
M. Ampere. 

The action which a current of electricity, from whatever source proceed- 
ing, exerts upon a magnetized needle is quite peculiar. The poles or centres 
of magnetic force are neither attracted nor repelled by the wire carrying the 
current, but made to move around the latter, by a force which may be 
termed tangential, and which is exerted in a direction perpendicular at once 
to that of the current, and to the line joining the pole and the wire. Both 
poles of the magnet being thus acted upon at the same time, and in contrary 
directions, the needle is forced to arrange itself across the current, so that 
its axis, or the line joining the poles, may be perpendicular to the wire ; and 
this is always the position which the needle will assume when the influence 
of terrestrial magnetism is in any way removed. This curious angular mo- 
tion may even be shown by suspending a magnet in such a way that one only 
of its poles shall be subjected to the current; a permanent movement of 
rotation will continue as long as the current is kept up, its direction being 
changed by altering the pole, or reversing the current. The moveable con- 
nections are made by mercury, into which the points of the conducting-wires 
dip. It is often of great practical consequence to be able to predict the 
direction in which a particular pole shall move by a given current, because 
in all galvanoscopes, and other instruments involving these principles, the 
movement of the needle is taken as an indication of the direction of the cir- 
culating current. And this is easily done by a simple mechanical aid to the 
memory: — Let the current be supposed to pass through a watch from the 
face to the back ; the motion of the north pole will be in the direction of the 
hands. Or a little piece of apparatus (fig. 72) may be used if reference ia 

Fig. 72. 



ZULa 



often requiied; this is a piece of pasteboard, or other suitable material, cut 
into the form of an arrow for indicating the current, crossed by a magnet 
having its poles marked, and arranged in the true position with respect to 
the current. The direction of the latter in the wire of the galvanoscope can 
at once be known by placing the representative magnet in the direction 
assumed by the needle itself. 

The common galvanoscope, consisting of a coil of wire having a compass- 
needle suspended on a point within it, is greatly improved by the addition 
of a second needle, as already in part described, and by a better mode of 
suspension, a long fibre of silk being used for the purpose. The two needles 
are of equal size ; and magnetized as nearly as possible to the same extent; 
they are then immovably fixed together, parallel, and with their poles op- 
posed, and hung with the lower needle in the coil and the upper one above 
it. The advantage gained is twofold; the system is astatic, unaffected, or 
nearly so, by the magnetism of the earth ; and the needles being both acted 
upon in the same manner by the current, are urged with much greater force, 



ELECTRICITY. 



101 



than Me alone would be. all the actions of every part of the coil being 
strictly concurrent. A divided circle is placed below the upper needle, by 
which the angular motion can be measured ; and the whole is enclosed in 
glass, to shield the needles from the agitation of the air. The arrangement 
is shown in fig. 73. 

Fig. 73. 



f 

P 



&K 



Fig. 74. 




The action between the pole and the wire is mutual, as^may be shown by 
rendering the wire itself moveable and placing a magnet in its vicinity : on 
completing the circuit, the wire will be put in motion, and, if the arrange- 
ment permits, rotate around the magnetic pole. 

A little consideration will show, that, from the 
peculiar nature of the electro-dynamic force, a 
wire carrying a current, bent into a spiral or 
helix, must possess the properties of an ordinary 
magnetized bar, its extremities being attracted 
and repelled by the poles of a magnet. Such is 
really found to be the case, as may be proved by a 
variety of arrangements, among which it will be 
sufficient to cite the beautiful little apparatus of 
Frofessor de la Rive. — A short wide glass tube 
(fig. 74) is fixed into a cork ring of considerable 
size ; a little voltaic battery, consisting of a single 
pair of copper and zinc plates, is fitted to the tube, and to these the ends 
of the spiral are soldered. On filling the tube with dilute acid and floating 
the whole in a large basin of water, the helix will be observed to arrange 
itself in the magnetic meridian, and on trial it will be found to obey a mag- 
net held near it in the most perfect manner, as long as the current circu 
lates. 

When an electric current is passed at right angles to a piece of iron or 
steel, the latter acquires magnetic polarity, either temporary or permanent 
as the case may be, the direction of the current determining the position of 
the poles. This effect is prodigiously increased by causing the current to 
circulate a number of times round the bar, which then acquires extraordi- 
nary magnetic power. A piece of soft iron, worked into the form of a horse- 
shoe (fig. 75), and surrounded by a coil of copper wire covered with silk or 
cotton for the purpose of insulation, furnishes an excellent illustration of 
the inductive energy of the current in this respect ; when the ends of the 
9* 



102 



ELECTRICITY 



Fig. 75. 



•wire are put into communication with a small voltaic battery of a single pair 
of plates, the iron instantly becomes so highly magnetic 
as to be capable of sustaining a very heavy weight. 

A current of electricity can thus develop magnetism 
in a transverse direction to its own ; in the same man- 
ner, magnetism can call into activity electric currents. 
If the two extremities of the coil of the electro-magnet 
above described be connected with a galvanoscope, and 
the iron magnetized by the application of a permanent 
steel horse-shoe magnet to the ends of the bar, a mo- 
mentary current will be developed in the wire, and 
pointed out by the movement of the needle. It lasts 
but a single instant, the needle returning after a few os- 
cillations to a state of rest. On removing the magnet, 
whereby the polarity of the iron is at once destroyed, a 
second current or wave will become apparent, but in the 
opposite direction to that of the first. By employing a 
very powerful steel magnet, surrounding its iron keeper 
or armature with a very long coil of wire, and then 
making the armature itself rotate in front of the faces 
of the magnet, so that its induced polarity shall be 
rapidly reversed, magneto-electric currents may be pro- 
duced, of such intensity as to give bright sparks and most powerful shocks, 
and exhibit all the phenomena of voltaic electricity. Fig. 76 represents a 
very powerful arrangement of this kind. 




Fig. 76. 




When two covereu wires are twisted together or laid side by side for some 
distance, and a current transmitted through the one, a momentary electrical 
wave will be induced in the other in the reverse direction, and on breaking 
connexion with the battery, a second single wave will become evident by the 
aid of the galvanoscope, in the same direction as that of the primary cur- 
rent. In the same way, when a current of electi-icity passes through one 
turn in a coil of wire, it induces two secondary currents in all the other 



ELECTRICITY. 103 

turns of the coil ; when the circuit is closed, the first is moving in the oppo- 
site direction to the primary current ; the second, when the circuit is broken, 
has a motion in the same direction as the primary current. The effect of 
the latter is added to that of the primary current. Hence, if a wire coil be 
made part of the conducting wire of a weak electric pile, and if the primary 
current, by means of an appropriate arrangement, is made and broken in 
rapid succession, we can increase in a remarkable manner the effects which 
are produced at the moment of breaking the circuit either at the place of 
interruption — such as the spark-discharges ; or in secondary closing-con- 
ductors, such as the action on the nerves or the decomposition of water. 

M. Ampere discovered in the course of his investigations a number of 
extremely interesting phenomena resulting from the action of electrical cur- 
rents on each other, which become evident when arrangements are made for 
giving mobility to the conducting wires. He found that, when two currents 
flowing in the same direction were made to approach each other, strong 
attraction took place between them, and when in opposite directions, an 
equally strong repulsion. — These effects, which are not difficult to demon- 
strate, have absolutely no relation that can be traced to ordinary electrical 
attractions and repulsions, from which they must be carefully distinguished ; 
they are purely dynamic, having to do with electricity in motion. M. 
Ampere founded upon this discovery a most beautiful and ingenious hypo- 
thesis of magnetic actions in general, which explains very clearly the influ- 
ence of the current upon the needle. 

The electricity exhibited under certain peculiar circumstances by a jet of 
steam, first observed by mere accident, but since closely investigated by Mr. 
Armstrong, and also by Mr. Faraday, is now referred to the friction, not of 
the pure steam itself, but of particles of condensed water, against the inte- 
rior of the exit-tube. It is very doubtful whether mere evaporation can cause 
electrical disturbance, and the hope first entertained that these phenomena 
would throw light upon the cause of electrical excitement in the atmosphere, 
is now abandoned. The steam is usually positive, if the jet-pipe be con- 
structed of wood or clean metal, but the introduction of the smallest trace 
of oily matter causes a change of sign. The intensity of the charge is, 
cceteris paribus, increased with the elastic force of the steam. By this means, 
effects have been obtained very far surpassing those of the most powerful 
plate electrical machines ever constructed. 



PART II. 

CHEMISTRY OF ELEMENTARY BODIES. 



The term element or elementary substance is applied in chemistry to those 
forms or modifications of matter which have hitherto resisted all attempts to 
decompose them. Nothing is ever meant to be affirmed concerning their 
real nature ; they are simply elements to us at the present time ; hereafter, 
by new methods of research, or by new combinations of those already pos- 
sessed by science, many of the substances which now figure as elements may 
possibly be shown to be compounds ; this has already happened, and may 
again take place. 

The elementary bodies, at present recognised, amount to sixty-two in 
number ; of these, about forty-seven belong to the class of metals. Several 
of these are of recent discovery and as yet very imperfectly known. The 
distinction between metals and non-metallic substances, although very con- 
venient for purposes of description, is entirely arbitrary, since the two classes 
graduate into each other in the most complete manner. 

It will be proper to commence with the latter and least numerous division. 
The elements are named as in the subjoined table, which, however, does not 
indicate the order in which they will be discussed. 



Non-metallic 
Elements. 

Oxygen 

Hydrogen 


Antimony 
Chromium 


Metals. 

Gold 
Aluminium 


Barium 

Strontium 


Nitrogen 


Vanadium 


Beryllium 


Calcium 


Chlorine 
Iodine 


Tungsten 
(or Wolfram) 


(or Glucinum) 
Zirconium 


Magnesium 
Zinc 


Bromine 


Molybdenum 


JVorium 


Cadmium 


Fluorine 


Tantalum 


Thorium 


Nickel 


Carbon 
Silicon 


(or Columbium) 
Niobium 


Yttrium 
Cerium 


Cobalt 
Copper 


Boron 
Sulphur 


Pelopium 
Titanium 


Erbium 
Terbium 


Iron 
Manganese 


Selenium 


Uranium 


Lantanum 


Lithium 


Phosphorus 


Platinum 
Palladium 


Didymium 
Bismuth 


Sodium 
Potassium 


Elements of interme- 
diate characters. 


Rhodium 
Iridium 


Tin 
Mercury 




Arsenic 


Ruthenium 


Silver 




Tellurium 


Osmium 


Lead 





(104) 



OXYGEN. 



105 



OXYGEN. 

Whatever plan of classification, founded on the natural relations of the 
elements, he adopted, in the practical study of chemistry, it will always be 
found most advantageous to commence with the consideration of the great 
constituents of the ocean and the atmosphere. 

Oxygen was discovered in the year 1774, by Scheele, in Sweden, and Dr. 
Priestley, in England, independently of each other, and described under the 
terms empyreal air and dephlogisticated air. The name oxygen l was given to 
it by Lavoisier some time afterwards. Oxygen exists in a free and uncom- 
bined state in the atmosphere, mingled with another gaseous body, nitrogen : 
no good direct means exist, however, for separating it from the latter, and, 
accordingly, it is always obtained for purposes of experiment by decom- 
posing certain of its compounds, which are very numerous. 

The red oxide of mercury, or red precipitate of the old writers, may be 
employed with this view. In this substance, the attraction which holds to- 
gether the mercury and the oxygen is so feeble, that simple exposure to heat 
suffices to bring about decomposition. The red precipitate is placed in a 
short tube of hard glass, to which is fitted a perforated cork, furnished with 
a piece of narrow glass tube, bent as in the figure. The heat of a spirit- 
lamp being applied to the substance, decomposition speedily commences, 
globules of metallic mercury collect in the cool part of the wide tube, which 
answers the purpose of a retort, while gas issues in considerable quantity from 
the apparatus. This gas is collected and examined by the aid of the pneu- 
matic trough, which consists of a vessel of water provided with a shelf, upon 
which stand the jars or bottles destined to receive the gas, filled with water 
and inverted. By keeping the level of the liquid above the mouth of the jar, 
the water is retained in the latter by the pressure of the atmosphere, and 
entrance of air is prevented. When brought over the extremity of the gas- 
delivering tube, the bubbles of gas rising through the water collect in the 
upper part of the jar and displace the liquid. As soon as one jar is filled. 

Fig. 77. 




1 From 6%vs, acid, and yzvvdw, I give rise to. 



106 



OXYGEN 



it may be removed, still keeping its mouth below the water-level, and an- 
other substituted. The whole arrangement is shown in fig. 77. 

The experiment described is more instructive as an excellent case of the 
resolution by simple means of a compound body into its constituents, than 
valuable as a source of oxygen gas. A better and more economical method 
is to expose to heat in a retort, or flask furnished with a bent tube, a por- 
tion of the salt called chlorate of potassa. A common Florence flask serves 
perfectly well, the heat of a spirit-lamp being sufficient. The salt melts 
and decomposes with ebullition, yielding a very large quantity of oxygen 
gas, which may be collected in the way above described. The first portion 
of the gas often contains a little chlorine. The white saline residue in the 
flask is chloride of potassium. This plan, which is very easy of execution, 
is always adopted when very pure gas is required for analytical purpose. 

A third method, very good when perfect purity is not demanded, is to heat 
to redness, in an iron retort or gun-barrel, the black oxide of manganese of 
commerce, which under these circumstances suffers decomposition, although 
not to the extent manifest in the red precipitate. 

If a little of the black oxide of manganese be finely powdered and mixed 
with chlorate of potassa, and this mixture heated in a flask or retort by a 
lamp, oxygen will be disengaged with the utmost facility, and at a far lower 
temperature than when the chlorate alone is used. All the oxygen comes 
from the chlorate, the manganese remaining quite unaltered. The materials 
should be well dried in a capsule before their introduction into the flask. 
This experiment affords an instance of an effect by no means rare, in which 
a body seems to act by its mere presence, without taking any obvious part 
in the change brought about. 

"Whatever method be chosen — and the same remark applies to the collec- 
tion of all other gases by similar means — the first portions of gas must be 
suffered to escape, or be received apart, as they are contaminated by the at- 
mospheric air of the apparatus. The practical management of gases is a 
point of great importance to the chemical student, and one with which he 
must endeavour to familiarize himself. The water-trough just described is 
one of the most indispensable articles of the laboratory, and by its aid all 
experiments on gases are carried on when the gases themselves are not sen- 
sibly acted upon by water. The trough is best constructed of japanned 
copper, the form and dimensions being regulated by the magnitude of the 
jars. It should have a firm shelf, so arranged as to be always about an inch 
below the level of the water, and in the shelf a groove should be made 
about half an inch in width, and the same in depth, to admit the extremity 
of the delivery-tube beneath the jar, which stands securely upon the shelf. 

Fig. 78. 




OXYGEN. 



107 



Fig. 79. 



When the pneumatic trough is required of tolerably large dimensions, it maj 
with great advantage have the form and disposition represented in the cux 
(fig. 78) ; one end of the groove spoken of, which crosses the shelf or shallow 
portion, is shown at a. 

Gases are transferred from jar to jar with the utmost facility, by firs* 
filling the vessel into which the gas is to be passed with water, inverting it, 
carefully retaining its mouth below the water-level, and then bringing be- 
neath it the aperture of the jar containing the gas. On gently inclining the 
latter, the gas passes by a kind of inverted decantation into the second 
vessel. When the latter is narrow, a funnel may be placed loosely in its 
neck, by which loss of gas will be found to be prevented. 

A jar wholly or partially filled with gas at the pneumatic trough may b 
removed by placing beneath it a shallow basin, 
or even a common plate (fig. 79), so as to 
carry away enough water to cover the edge of 
the jar; and gas, especially oxygen, may be 
so preserved for many hours without material 
injury. 

Gas-jars are often capped at the top, and 
fitted with a stop-cock for transferring to blad- 
ders or caoutchouc bags. When such a vessel 
is to be filled with water, it may be slowly 
sunk in an upright position in the well of the 
pneumatic trough, the stop-cock being open to 
allow the air to escape, until the water reaches 
the brass cap. The cock is then to be turned, 
and the jar lifted upon the shelf and filled with 
gas in the usual way. If the trough be not 
deep enough for this manoeuvre, the mouth 
may be applied to the stop-cock, and the vessel 

filled by sucking out the air until the water rises to the cap. In all cases it 
is proper to avoid as much as possible wetting the stop-cocks, and other brass 
apparatus. 

Mr. Pepys contrived some years ago an admirable piece of apparatus for 
storing and retaining large quantities" of gas. 
It consists of a drum or reservoir of sheet 
copper (fig. 80), surmounted by a shallow 
trough or cistern, the communication be- 
tween the two being made by a couple of 
tubes, a b, furnished with cocks, fh, one of 
which passes nearly to the bottom of the 
drum, as shown in the sectional sketch. A 
short wide open tube, c, is inserted obliquely 
near the bottom of the vessel, into which a 
plug may be tightly screwed. A stop-cock, 
ff, near the top, serves to transfer gas to a 
bladder or tube apparatus. A glass water- 
guage, de, affixed to the side of the drum, 
and communicating with both top and bot- 
tom, indicates the level of the liquid within. 

To use the gas-holder, the plug is first to 
be screwed into the lower opening, and the 
drum completely filled with water. All 
three stop-cocks are then to be closed, and 
the plug removed. The pressure of the atmosphere retains the water in the 
gas holder, and if no air-leakage occur, the escape of water is inconsider- 




Fig. 




108 O X Y G E N . 

able. The extremity of the delivery-tube is now to be well pushed through, 
the open aperture into the drum, so that the bubbles of gas rise without hin- 
drance to the upper part, displacing the water, which flows out in the same 
proportion into a vessel placed for its reception. When the drum is filled, or 
enough gas has been collected, the tube is withdrawn, and the plug screwed 
into its place. 

When a portion/ of the gas is to be transferred to a jar, the latter is 
filled with water at the pneumatic trough, carried by the help of a basin or 
plate to the cistern of the gas-holder, and placed over the shorter tube. Oi 
opening the cock of the neighbouring tube, the hydrostatic pressure of th 1 
column of water will cause condensation of the gas, and increase its elastic 
force, so that on gently turning the cock beneath the jar, it will ascend into 
the latter in a rapid stream of bubbles. The jar, when filled, may again 
have the plate slipped beneath it, and be removed without difficulty. 

Oxygen, when free or uncombined, is only known in the gaseous state, all 
attempts to reduce it to the liquid or solid condition by cold and pressure 
having completely failed. It is, when pure, colourless, tasteless, and in- 
odorous ; it is the sustaining principle of animal life, and of all the ordinary 
phenomena of combustion 

Bodies which burn in the air burn with greatly increased splendour in 
oxygen gas. If a taper be blown out, and then introduced while the wick 
remains red-hot, it is instantly rekindled : a slip of wood or a match is re- 
lighted in the same manner. This effect is highly characteristic of oxygen, 
there being but one other gas which possesses the same property; and this 
is easily distinguished by other means. The experiment with the match is 
also constantly used as a rude test of the goodness of the gas when it is about 
to be collected from the retort, or when it has stood some time in contact 
with water exposed to air. 

When a bit of charcoal is affixed to a wire, and plunged with a single 
point red-hot into ajar of oxygen, it burns with great brilliancy, throwing 
off beautiful scintillations, until, if the oxygen be in excess, it is completely 
consumed. An iron wire, or, still better, a steel watch-spring, armed at its 
extremity with a bit of lighted amadou, and introduced into a vessel of good 
gas, exhibits a most beautiful appearance of combustion. If the experiment 
be made in ajar standing on a plate, the fused globules of black oxide of 
iron fix themselves in the glaze of the latter, after falling through a stratum 
of water half an inch in depth. Kindled sulphur burns with great beauty 
in oxygen, and phosphorus, under similar circumstances, exhibits a splendour 
which the eye is unable to support. 

In these and many other similar cases which might be mentioned, the same 
ultimate effect is produced as in atmospheric air ; the action is, however, 
more energetic from the absence of the gas which in the air dilutes the 
oxygen, and enfeebles its chemical powers. The process of respiration in ani- 
mals is an effect of the same nature as common combustion. The blood con- 
tains substances which slowly burn by the aid of the oxygen thus introduced 
into the system. When this action ceases, life becomes extinct. 

Oxygen is, bulk for bulk, a little heavier than atmospheric air, which is 
usually taken as the standard of unity of specific gravity among gases. Its 
specific gravity is expressed by the number 1-1057; • 100 cubic inches at 60° 
(15°-5C). and under the mean pressure of the atmosphere, that is, 30 inches 
of mercury, weigh 34-29 grains. 

It has been already remarked, that to determine with the last degree of 
accuracy the specific gravity of a gas, is an operation of very great practical 
difficulty, but at the same time of very great importance. There are several 



Dumas, Arm. Chiin. et Phys., 3d series, iii. 275. 



OXYGEN. 109 

methods which may be adopted for this purpose ; the one below described 
appears, on the whole, to be the simplest and best. It requires, however, 
the most scrupulous care, and the observance of a number of minute pre- 
cautions, which are absolutely indispensable to success. 

The plan of the operation is as follows : A large glass globe is to be filled 
with the gas to be examined, in a perfectly pure and dry state, having a 
known temperature, and an elastic force equal to that of the atmosphere at 
the time of the experiment. The globe so filled is to be weighed. It is 
then to be exhausted at the air-pump as far as convenient, and again 
weighed. Lastly, it is to be filled with dry air, the temperature and pres- 
sure of which are known, and its weight once more determined. On the 
supposition that the temperature and elasticity are the same in both cases, 
the specific gravity is at once obtained by dividing the weight of the gas by 
that of the air. 

The globe or flask must be made very thin, and fitted with a brass cap, 
surmounted by a small but excellent stop-cock. A delicate thermometer 
should be placed in the inside of the globe, secured to the cap. The gas 
must be generated at the moment, and conducted at once into the previously 
exhausted vessel, through a long tube filled with fragments of pumice moist- 
ened with oil of vitriol, or some other extremely hygroscopic substance, by 
which it is freed from all moisture. As the gas is necessarily generated 
under some pressure, the elasticity of that contained in the filled globe will 
slightly exceed the pressure of the atmosphere ; and this is an advantage, 
since by opening the stop-cock for a single instant when the globe has 
attained an equilibrium of temperature, the tension becomes exactly that of 
the air, so that all barometrical correction is avoided, unless the pressure of 
the atmosphere should sensibly vary during the time occupied by the expe- 
riment. It is hardly necessary to remark, that the greatest care must also 
be taken to purify and dry the air used as the standard of comparison, and 
to bring both gas and air as nearly as possible to the same temperature, to 
obviate the necessity of a correction, or at least to diminish almost to nothing 
the errors involved by such a process. 

The compounds formed by the direct union of oxygen with other bodies, 
bear the general name of oxides ; these are very numerous and important. 
They are conveniently divided into three principal groups or classes. The 
first division contains all those oxides which resemble in their chemical rela- 
tions, potassa, soda, or the oxide of silver or of lead ; these are denominated 
alkaline or basic oxides, or sometimes salifiable bases. The oxides of the 
second group have properties exactly opposed to those of the bodies men- 
tioned ; oil of vitriol and phosphoric acid may be taken as the types or repre- 
sentatives of the class : they are called acids, and tend strongly to unite 
with the basic oxides. When this happens, what is called a salt is generated 
as sulphate of potassa, or phosphate of silver, each of these substances be- 
ing compounded of a pair of oxides, one of which is highly basic and the 
other highly acid. 

Then there remains a third group of what may be termed neutral oxides, 
from their little disposition to enter into combination. The black oxide of 
manganese, already mentioned, is an excellent example. 

It very frequently happens that a body is capable of uniting with oxygen 
in several proportions, forming a series of oxides, to which it is necessary 
to give distinguishing names. The rule in such cases is very simple, at least 
when the oxides of the metals are concerned. In such a series it is always 
found that one out of the number has a strongly-marked basic character ; to 
this the term protoxide is given. The compounds next succeeding receive 
the names of binoxide or deut oxide, teroxide or tritoxide, &c, from the Latin or 
Greek numerals, the different grades of oxidation being thus indicated. If 
10 



110 HYDROGEN. 

there be a compound between the protoxide and binoxide, the name sesqui- 
oxide is usually applied. So it is usual to call the highest oxide, not having 
distinctly acid characters, peroxide, from the Latin prefix, signifying excess. 
Any compound containing less oxygen than the protoxide, is called a sub- 
oxide. Superoxide or hi/peroxide are words sometimes used instead of per- 
oxide. 
t Ozone. — It has long been known that dry oxygen, or atmosphei'io air, 
• when exposed to the passage of a series of electric sparks, emits a peculiar 
and somewhat metallic odour. The same odour may be imparted to moist 
oxygen, by allowing phosphorus to remain for some time in it. A more 
accurate examination of this odorous air has shown that, in addition to the 
smell, it assumes several properties not exhibited by pure oxygen. One of 
its most curious effects is the liberation of iodine from iodide of potassium. 
The oxygen thus altered has been the subject of many researches lately, 
particularly by Prof. Schoenbein, of Basel, who proposed the name of ozone 1 
for it. The true nature of ozone, however, is still unknown, most probably 
it is a peculiar modification of oxygen. 

HYDROGEN. 

Hydrogen is always obtained for experimental purposes by deoxidizing 
water, of which it forms the characteristic component. 2 

If a tube of iron or porcelain, containing a quantity of filings or turnings 
of iron, be fixed across a furnace, and its middle portion be made red-hut, 
and then the vapour of water transmitted over the heated metal, a large 
quantity of permanent gas will be disengaged from the tube, and the iron 
will become converted into oxide, and acquire an increase in weight. The 
gas is hydrogen ; it may be collected over water and examined. 

When zinc is put into water, chemical action of the liquid upon the metal 
is imperceptible ; but if a little sulphuric acid be added, decomposition of 
the water ensues, the oxygen unites with the zinc, forming oxide of zinc, 
which is instantly dissolved by the acid, while the hydrogen, previously in 
union with the oxygen, is disengaged in the gaseous form. The reaction is 
represented in the subjoined diagram. 

Water / Hydrogen Free. 

t Oxygen. ._ 

Zinc ' — oxide of zinc | Sulphate of 

Sulphuric acid /oxide of zinc 

It is not easy to explain the fact of the ready decomposition of water by 
zinc, in presence of an acid or other substance which can unite with the 
oxide so produced ; it is, however, a kind of reaction of very common oc- 
currence in chemistry. 

The simplest method of preparing the gas is the following. — A wide-necked 
bottle is chosen, and fitted with a sound cork (fig. 81). perforated by two 
holes for the reception of a small tube-funnel reaching nearly to the bottom 
of the bottle, and a piece of bent glass tube to convey away the disengaged 
gas. Granulated zinc, or scraps of the malleable metal, are put into the 
bottle, together with a little water, and sulphuric acid slowly added by the 
funnel, the point of which should dip into the liquid. The evolution of gas 
is easily regulated by the supply of acid, and when enough has been dis- 
charged to expel the air of the vessel, it may be collected "over water into a 
jar, or passed into a gas-holder. In the absence of zinc, filings of iron 01 
amall nails may be used, but with less advantage. 

1 From o£o>, T smell. 

& llcnce the name, from fiSvp, water, find ytvvuu). 



HYDROGEN. 



Ill 



Fig. 81. 




A little practice will soon enable the 
pupil to construct and arrange a variety 
of useful forms of apparatus, in which 
bottles and other articles always at 
hand, are made to supersede more 
costly instruments. Glass tube, pur- 
chased by weight of the maker, may be 
cut by scratching with a file, and then 
applying a little force with both hands. 
It may be softened and bent, when of 
small dimensions, by the flame of a 
spirit-lamp, or even a candle or gas-jet. 
Corks may be perforated by a heated 
wire, and the hole rendered smooth and 
cylindrical by a round file, or the in- 
genious cork-borer of Dr. Mohr, now 
to be had of most instrument makers, 
may be used instead. Lastly, in the 
event of bad fitting, or unsoundness in 
the cork itself, a little yellow wax 
melted over the surface, or even a little grease applied with the finger, 
renders it sound and air-tight, when not exposed to heat. 

Hydrogen is colourless, tasteless, and inodorous, when quite pure. To 
obtain it in this condition, it must be prepared from the purest zinc that can 
be obtained, and passed in succession through solutions of potassa and nitrate 
of silver. When prepared from commercial zinc, it has a slight smell, which 
is due to impurity, and when iron has been used, the odour becomes very 
strong and disagreeable. It is inflammable, burning when kindled with a 
pale yellowish flame, and evolving much heat, but very little light. The 
result of the combustion is water. It is even less soluble in water than 
oxygen, and has never been liquefied. Although destitute of poisonous pro- 
perties, it is incapable of sustaining life. 

In point of specific gravity, hydrogen is the lightest substance known ; 
Dumas and Boussingault place its density between 0-0691 and 
0-0695 ;* hence 100 cubic inches will weigh, under ordinary 
circumstances of pressure and temperature, 2-14 grains. 

When a gas is much lighter or much heavier than atmospheric 
air, it may often be collected and examined without the aid of 
the pneumatic trough. A bottle or narrow jar maybe filled 
with hydrogen without much admixture of air, by inverting it 
over the extremity of an upright tube delivering the gas (fig. 
82). In a short time, if the supply be copious, the air will 
be wholly displaced and the vessel filled. It may now be 
removed, the vertical position being carefully retained, and 
closed by a stopper or glass plate. If the mouth of the jar be 
wide, it must be partially closed by a piece of card-board 
during the operation. This method of collecting gases by 
displacement is often extremely useful. Hydrogen was for- 
merly used for filling air-balloons, being made for the purpose 
on the spot from zinc or iron and dilute sulphuric acid. Its use 
is now superseded by that of coal-gas, which may be made very light by 
employing a high temperature in the manufacture. Although far inferior 
to pure hydrogen in buoyant power, it is found in practice to possess advan- 
tages over that substance, while its greater density is easily compensated 
by increasing the magnitude of the balloon. 



Fig. 82. 




Ann. Ciiim. et Tbys. 3d. series, viii. £)1. 



112 HYDROGEN. 

There is a very remarkable property enjoyed by gases and vapours in 
general, which is seen in a high degree of intensity in the case of hydrogen , 
this is what is called diffusive power. If two bottles, containing gases which 
do not act chemically upon each other at common temperatures, be connected 
by a narrow tube and left for some time, these will be found, at the expira- 
tion of a certain period, depending much upon the narrowness of the tube 
and its length, uniformly mixed, even though the gases differ greatly in 
density, and the system has been arranged in a vertical position, with the 
heaviest gas downwards. Oxj^gen and hydrogen can thus be made to mix, 
in a few hours, against the action of gravity, through a tube a yard in length, 
and not more than one-quarter of an inch in diameter ; and the fact is true 
of all other gases which are destitute of direct action upon each other. 

If a vessel be divided into two portions by a diaphragm or partition of 
porous earthenware or dry plaster of Paris, and each half filled with a dif- 
ferent gas, diffusion will immediately commence through the pores of the 
dividing substance, and will continue until perfect mixture has taken place. 
All gases, however, do not permeate the same porous body, or, in other 
words, do not pass through narrow orifices with the same degree of facility. 
Professor Graham, to whom we are indebted for a very valuable investigation 
of this interesting subject, has established the existence of a very simple 
relation between the rapidity of diffusion and the density of the gas, which 
is expressed by saying that the diffusive power varies inversely as the square 
root of the density of the gas itself. Thus, in the experiment supposed, if 
one half of the vessel be filled with hydrogen and the 
Fig. 83. other half with oxygen, the two gases will penetrate the 

diaphragm at very different rates ; four cubic inches of hy- 
drogen will pass into the oxygen side, while one cubic inch 
of oxygen travels in the opposite direction. The densities 
of the two gases are to each other in the proportion of 1 to 
16 ; their relative rates of diffusion will be inversely as the 
square roots of tjiese numbers, or 4 to 1. 

By making the diaphragm of some flexible material, as 
a piece of membrane, the accumulation of the lighter gas 
on the side of the heavier may be rendered evident by the 
bulging of the membrane. The simplest and most striking 
method of making the experiment is by the use of Profes- 
sor Graham's diffusion-tube (fig. 83). This is merely a 
piece of wide glass tube ten or twelve inches in length, 
having one of its extremities closed by a plate of plaster 
of Paris about half an inch thick, and well dried. When 
the tube is filled by displacement with hydrogen, and then 
set upright in a glass of water, the level of the liquid rises 
in the tube so rapidly, that its movement is apparent to the eye, and speedily 
attains a height of several inches above the water in the glass. The gas is 
actually rarefied by its superior diffusive power over that of the external 
air. 

It is impossible to over-estimate the importance in the great economy of 
Nature, of this very curious law affecting the constitution of gaseous bodies ; 
it is the principal means by which the atmosphere is preserved in an uniform 
state, and the accumulation of poisonous gases and exhalations in towns and 
other confined localities prevented. 

A distinction must be carefully drawn between real diffusion through small 
apertures, and the apparently similar passage of gas through wet or moist 
membranes and other substances, which is really due to temporary liquefac- 
tion or solution of the gas, and is an effect completely different from diffu- 
sion, properly so called. For example, the diffusive power of carbonic acid 




HYDROGEN. 



113 



into atmospheric air is very small, but it passes into the latter through a wet 
bladder with the utmost ease, in virtue of its solubility in the water with 
which the membrane is moistened. It is by such a process that the function 
of respiration is performed ; the aeration of the blood in the lungs, and the 
disengagement of the carbonic acid, are effected through wet membranes ; 
the blood is never brought into actual contact with the air, but receives its 
supply of oxygen, and disembarrasses itself of carbonic acid by this kind 
of spurious diffusion. 

The high diffusive power of hydrogen against air renders it impossible to 
retain that gas for any length of time in a bladder or caoutchouc bag : it is 
even unsafe to keep it long in a gas-holder, lest it should become mixed with 
air by slight accidental leakage, and be rendered explosive. 1 

It has been stated, that, although the light emitted by the flame of pure 
hydrogen is exceedingly feeble, yet the temperature of the flame is very 
high. This temperature may be still farther exalted by previously mixing 
the hydrogen with as much oxygen as it requires for combination, that is, 
as will presently be seen, exactly half its volume. Such a mixture burns 
like gunpowder, independently of the external air. "When raised to the 
requisite temperature for combination, the two gases unite with explosive 
violence. If a strong bottle, holding not more than half a pint, be filled 
with such a mixture, the introduction of a lighted match or red-hot wire 
determines in a moment the union of the gases. By certain precautions, a 
mixture of oxygen and hydrogen can be burned at a jet without communi- 
cation of fire to the contents of the vessel ; the flame is in this case solid. 

A little consideration will show, that all ordinary flames burning in the 
air or in pure oxygen are, of necessity, hollow. The act of combustion is 
nothing more than the energetic union of the substance burned with the 
surrounding oxygen : and this union can only take place at the surface of 
the burning body. Such is not the case, however, with the flame now under 
consideration ; the combustible and the oxygen are already mixed, and only 
require to have their temperature a little raised to cause them to combine in 
every part. The flame so produced is very different in phy- 
sical characters from that of a simple jet of hydrogen or any 
other combustible gas ; it is long and pointed, and very re- 
markable in appearance. 

The safety-jet of Mr. Hemming, the construction of which 
involves a principle not yet discussed, may be adapted to a com- 
mon bladder containing the mixture, and held under the arm, 
and the gas forced through the jet by a little pressure. 
Although the jet, properly constructed, is believed to be safe, 
it is best to use nothing stronger than a bladder, for fear of 
injury in the event of an explosion. The gases are often con- 
tained in separate reservoirs, a pair of large gas-holders, for 
example, and only suffered to mix in the jet itself, as in the 
contrivance of Professor Daniell ; in this way all danger is 
avoided. The eye speedily becomes accustomed to the pecu- 
liar appearance of the true hydro-oxygen flame, so as to 
permit the supply of each gas to be exactly regulated by 
suitable stop-cocks attached to the jet (fig. 84). 

A piece of thick platinum wire introduced into the flame 
of the hydro-oxygen blowpipe melts with the greatest ease ; 
a watch-spring or small steel file burns with the utmost 
brilliancy, throwing off showers of beautiful sparks ; an in- 

1 Professor Graham has since published a very ezteni-ive series of researches on the pas 
Fa.cre of .eases through narrow tubes, which will be found ia detail in the Philosophical Trans- 
actions for 1846, p. 573. 

10* 




114 HYDROGEN. 

combustible oxidized body, as magnesia or lime, becomes so intensely ig- 
nited, as to glow with a light insupportable to the eye, and to be susceptible 
of employment as a most powerful illuminator, as a substitute for the sun's 
rays in the solar microscope, and for night-signals in trigonometrical surveys. 
If a long glass tube, open at both ends, be held over a jet of hydro- 
Fig. 85. g en (fig. g5)^ a series of musical sounds are sometimes produced by 
the partial extinction and rekindling of the flame by the ascending 
current of air. These little explosions succeed each other at regular 
intervals, and so rapidly as to give rise to a musical note, the pitch 
depending chiefly upon the length and diameter of the tube. 

Although oxygen and hydrogen may be kept mixed at common 
temperatures for any length of time without combination taking 
place, yet, under particular circumstances, they unite quietly and 
without explosion. Some years ago, Professor Dobereiner, of Jena, 
made the curious observation, that finely-divided platinum possessed 
the power of determining the union of the gases ; and, more recently, 
Mr. Faraday has shown that the state of minute division is by no 
means indispensable, since rolled plates of the metal had the same 
property, provided their surfaces were absolutely clean. Neither is 
the effect strictly confined to platinum ; other metals, as palladium 
and gold, and even stones and glass, enjoy the same property, 
although to a far inferior degree, since they often require to be aided 
by a little heat. When a piece of platinum foil, which has been 
cleaned by hot oil of vitriol and thorough washing with distilled 
water, is thrust into a jar containing a mixture of oxygen and hydro- 
gen standing over water, combination of the two gases immediately 
begins, and the level of the water rapidly rises, the platinum 
becoming so hot, that drops of water accidentally falling upon it 
enter into ebullition. If the metal be very thin and exceedingly clean, and 
the gases very pure, then its temperature rises after a time to actual redness, 
and the residue of the mixture explodes. But this is an effect altogether 
accidental, and dependent upon the high temperature of the platinum, which 
high temperature has been produced by the preceding quiet combination of 
the two bodies. When the platinum is reduced to a state of division, and 
its surface thereby much extended, it becomes immediately red-hot in a 
mixture of hydrogen and oxygen, or hydrogen and air ; a jet of hydrogen 
thrown upon a little of the spongy metal, contained in a glass or capsule, 
becomes at once kindled, and on this principle machines for the production 
of instantaneous light have been constructed. These, however, only act 
well when constantly used ; the spongy platinum is apt to become damp by 
absorption of moisture from the air, and its power is then for the time lost. 
The best explanation that can be given of these curious effects, is to sup- 
pose that solid bodies in general have, to a greater or less extent, the pro- 
perty of condensing gases upon their surfaces, and that this faculty is 
enjoyed pre-eminently by certain of the non-oxidizable metals, as platinum 
a nd gold. Oxygen and hydrogen may thus, under these circumstances, be 
brought, as it were, within the sphere of their mutual attractions by a tem- 
porary increase of density, whereupon combination ensues. 

Coal-gas and ether or alcohol vapour may be made to exhibit the phenome- 
non of quiet oxidation under the influence of this remarkable surface-action. 
A close spiral of slender platinum wire, a roll of thin foil, or even a common 
platinum crucible, heated to dull redness, and then held in a jet of coal-gas, 
becomes strongly ignited, and remains in that state as long as the supply of 
mixed gas and air is kept up, the temperature being maintained b}' the heat 
disengaged in the act of union. Sometimes the metal becomes white-hot, 
and then the gas takes fire. 




HYDROGEN. 115 

A very pleasing experiment may be made by attaching such a coil ot wire 
to a card, and suspending it in a glass containing a few drops of ether 
(fig. 86), having previously made it red-hot in the flame 
of a spirit-lamp. The wire continues to glow until the Fig. 86. 

oxygen of the air is exhausted, giving rise to the pro- 
duction of an irritating vapour which attacks the eyes. 
The combustion of the ether is in this case but partial ; 
a portion of its hydrogen is alone removed, and the 
whole of the carbon left untouched. 

A coil of thin platinum wire may be placed over the 
wick of a spirit-lamp, or a ball of spongy platinum sus- 
tained just above the cotton ; on lighting the lamp, and 
then blowing it out as soon as the metal appears red-hot, 
slow combustion of the spirit drawn up by the capillarity 
of the wick will take place, accompanied by the pungent 
vapours just mentioned, which may be modified, and 
even rendered agreeable, by dissolving in the liquid some 
sweet-smelling essential oil or resin. 

Hydrogen forms numerous compounds with other bodies, although it is 
greatly surpassed in this respect not only by oxygen, but by many of the 
other elements. The chemical relations of hydrogen tend to place it beside 
the metals. The great discrepancy in physical properties is perhaps more 
apparent than real. Hydrogen is yet unknown in the solid condition, while, 
on the other hand, the vapour of the metal mercury is as transparent and 
colourless as hydrogen itself. This vapour is only about seven times heavier 
than atmospheric air, so that the difference in this respect is not nearly so 
great as that in the other direction between air and hydrogen. 

There are two oxides of hydrogen, namely, water, and a very peculiar 
substance, discovered in the year 1818, by M. Thenard, called binoxide of 
hydrogen. 

It appears that the composition of water was first demonstrated in the 
year 1781, by Mr. Cavendish, 1 but the discovery of the exact proportions in 
which oxygen and hydrogen unite in generating that most important com- 
pound has from time to time to the present day occupied the attention of 
some of the most distinguished cultivators of chemical science. There are 
two distinct methods of research in chemistry : the analytical, or that in which 
the compound is resolved into its elements, and the synthetical, in which the 
elements are made to unite and produce the compound. The first method 
is of much more general application than the second, but in this particular 
instance both may be employed, although the results of the synthesis are 
most valuable. 

The most elegant example of analysis of water would probably be found 
in its decomposition by voltaic electricity. When water is acidulated so as 
to render it a conductor, and a portion interposed between a pair of platinum 
plates connected with the extremities of a voltaic apparatus of moderate 
power, decomposition of the liquid takes place in a very interesting 
manner ; oxygen, in a state of perfect purity, is evolved from the water in 
contact with the plate belonging to the copper end of the battery, and 
hydrogen, equally pure, is disengaged at the plate connected with the zinc 
extremity, the middle portions of liquid remaining apparently unaltered 
By placing small graduated jars over the platinum plates, the gases can be 

1 A claim to the discovery of the composition of water on behalf of Mr. James Watt, ha* 
been very strongly uru;ed, and supported by such evidence that the reader of the controversy 
may be led to the conclusion that the discovery was made by both parties nearly aimulta- 
ne >usly, and unknown to each other. 



116 



HYDROGEN. 



Fie. 87. 



me 




collected, and their quantities determined. 
Fig. 87 will show at a glance the whole 
arrangement; the conducting wires pass 
through the bottom of the glass cup, and 
thence to the battery. 

When this experiment has been con- 
tinued a sufficient time, it will be found 
that the volnme of the hydrogen is a very 
little above twice that of the oxygen ; 
were it not for the accidental circumstance 
of oxygen being sensibly more soluble in 
water than hydrogen, the proportion of 
two to one by measure would come out 
exactly. 

Water, as Mr. Grove has lately shown, 
is likewise decomposed into its constituents 
by heat. The effect is produced by intro- 
ducing platinum balls, ignited by electricity or other means, 
Into water or steam. The two gases are, however, obtained 
in very small quantities at a time. 

When oxygen and hydrogen, both as pure as possible, are 
mixed in the proportions mentioned, passed into a strong glass 
tube filled with mercury, and exploded by the electric spark, 
all the mixture disappears, and the mercury is forced up into 
the tube, filling it completely. The same experiment may be 
made with the explosion-vessel or eudiometer of Mr. Caven- 
dish. (Fig. 88.) The instrument is exhausted at the air- 
pump, and then filled from a capped jar with the mixed 
gases ; on passing an electric spark by the wires shown at a, 
explosion ensues, and the glass becomes bedewed with 
moisture, and if the stop-cock be then opened under water, 
the latter will rush in and fill the vessel, leaving merely a 
bubble of air, the result of an imperfect exhaustion. 

The process upon which most reliance is placed is that in 
which pure oxide of copper is reduced at a red heat by hy- 
drogen, and the water so formed collected and weighed. This 
oxide suffers no change by heat alone, but the momentary 
contact of hydrogen, or any common combustible matter at a high 
perature, suffices to reduce a corresponding portion to the metallic 
Fig. 89 will serve to convey some idea of the arrangement adopted 
searches of this kind. 




tem- 
state. 
in re- 



Fig. 




2N=» 



A copious supply of hydrogen is procured by the action of dilute sul- 
phuric acid upon the purest zinc that can be obtained ; the gas is made to 
pass in succession through solutions of silver and strong caustic potassa, by 
which its purification is completed. After this, it is conducted tlirorgh a 



HYDROGEN. IT J 

tube three or four feet in length, filled with fragments of pumice-stone 
steeped in concentrated oil of vitriol, or with anhydrous phosphoric acid. 
These substances have such an extraordinary attraction for aqueous vapour s 
that they dry the gas completely during its transit. The extremity of this 
tube is shown at a. The dry hydrogen thus arrives at the part of the appa- 
ratus containing the oxide of copper, represented at b ; this consists of a 
two-necked flask of very hard white glass, maintained at a red heat by a 
spirit-lamp placed beneath. As the decomposition proceeds, the water pro- 
duced by the reduction of the oxide begins to condense in the second neck 
of the flask, whence it drops into the receiver c, provided for the purpose. 
A second desiccating tube prevents the loss of aqueous vapour by the cur- 
rent of gas which passes in excess. 

Before the experiment can be commenced, the oxide of copper, the purity 
of which is well ascertained, must be heated to redness for some time in a 
current of dry air ; it is then suffered to cool, and very carefully weighed 
with the flask. The empty receiver and second drying tube are also weighed, 
the disengagement of gas set up, and when the air has been displaced, heat 
slowly applied to the oxide. The action is at first very energetic ; the oxide 
often exhibits the appearance of ignition ; as the decomposition proceeds, it 
becomes more sluggish, and requires the application of a good deal of heat 
to effect its completion. 

When the process is at an end, and the apparatus perfectly cool, the 
stream of gas is discontinued, dry air is drawn through the whole arrange- 
ment, and, lastly, the parts are disconnected and re-weighed. The loss of 
the oxide of copper gives the oxygen ; the gain of the receiver and its dry- 
ing-tube indicates the water, and the difference between the two, the hy- 
drogen. 

A set of experiments, made in Paris in the year 1820, 1 by MM. Dulong 
and Berzelius, gave as a mean result for the composition of water by weight, 
8-009 parts oxygen to 1 part hydrogen ; numbers so nearly in the proportion 
of 8 to 1, that the latter have usually been assumed to be true. 

Quite recently the subject has been re-investigated by M. Dumas, 2 with 
the most scrupulous precision, and the above supposition fully confirmed. 
The composition of water may therefore be considered as established: it 
contains by weight 8 parts oxygen to 1 part hydrogen, and by measure, 1 
volume oxygen to 2 volumes hydrogen. The densities of the gases, as al- 
ready mentioned, correspond very closely with these results. 

The physical properties of water are too well known to need lengthened 
description; it is, when pure, colourless and transparent, destitute of taste 
and odour, and an exceedingly bad conductor of electricity of low tension. 
It attains its greatest density towards 40° (4°-5C), freezes at 32° (0°C), and 
boils under the pressure of the atmosphere at or near 212° (100°C). It 
evaporates at all temperatures. One cubic inch at 62° (16°-7C) weighs 
2-52-45 grains. It is 815 times heavier than air; an imperial gallon weighs 
70,000 grains or 10 lb. avoirdupois. To all ordinary observation, water is 
incompressible ; very accurate experiments have nevertheless shown that it 
does yield to a small extent when the power employed is very gf eat ; the 
diminution of volume for each atmosphere of pressure being about 51-mil- 
lionths of the whole. 

Clear water, although colourless in small bulk, is blue like the atmosphere 
when viewed in mass. This is seen in the deep ultramarine tint of the ocean, 
and perhaps in a still more beautiful manner in the lakes of Switzerland 
and other Alpine countries, and in the rivers which issue from them ; the 
Brightest admixture of mud or suspended impurity destroying the effect. 

1 Ann. Chim. et Phys. xv. 386. 3 Ann. Chim. et Phys. 3rd series, viii. 189. 



118 HYDROGEN. 

The same magnificent colour is visible in the fissures and caverns found in 
the ice of the glaciers, which is usually extremely pure and transparent 
within, although foul upon the surface. 

Steam, or vapour of water, in its state of greatest density at 212° (100°C), 
compared with air at the same temperature, and possessing an equal elastic 
force, has a specific gravity expressed by the fraction of 0-625. In this con- 
dition, it may be represented as containing, in every two volumes, two 
vohimes of hydrogen, and one volume of oxygen. 

Water seldom or never occurs in nature in a state of perfect purity ; even 
the rain which falls in the open country, contains a trace of ammoniacal salt, 
while rivers and springs are invariably contaminated to a greater or less 
extent with soluble matters, saline and organic. Simple filtration through a 
porous stone or a bed of sand will separate suspended impurities, but dis- 
tillation alone will free the liquid from those that are dissolved. In the pre- 
paration of distilled water, which is an article of large consumption in the 
scientific laboratory, it is proper to reject the first portions which pass over, 
and to avoid carrying the distillation to dryness. The process may be con- 
ducted in a metal still furnished with a worm or condenser of silver or tin ; 
lead must not be used. 

The ocean is the great recipient of the saline matter carried down by the 
rivers which drain the land ; hence the vast accumulation of salts. The 
following table will serve to convey an idea of the ordinary composition of 
sea-water ; the analysis is by Dr. Schweitzer, 1 of Brighton, the water being 
that of the Channel : — 

1000 grains contained 

Water 964-745 

Chloride of sodium 27-059 

Chloride of potassium 0-766 

Chloride of magnesium 3-666 

Bromide of magnesium 0-029 

Sulphate of magnesia 2-296 

Sulphate of lime 1-406 

Carbonate of lime 0-033 

Traces of iodine and ammoniacal salt 

1000-000 

Its specific gravity was found to be 1-0274 at 60° (15°-5C). 

Sea-water is liable to variations of density and composition by the influence 
of local causes, such as the proximity of large rivers or masses of melting 
ice, and other circumstances. 

Natural springs are often impregnated to a great extent with soluble sub- 
stances derived from the rocks they traverse ; such are the various mineral 
waters scattered over the whole earth, and to w r hich medicinal virtues are 
attributed. Some of these hold protoxide of iron in solution, and are effer- 
vescent from carbonic acid gas ; others are alkaline, probably from traver- 
sing rocks of volcanic origin; some contain a very notable quantity of iodine 
or bromine. Their temperatures also are as variable as their chemical 
nature. A tabular notice of some of the most remarkable of these waters 
will be found in the Appendix. 

Water enters into direct combination with other bodies, forming a class 
of compounds called hydrates ; the action is often very energetic, much heat 
being evolved, as in the case of the slaking of lime, which is really the pro- 
duction of a hydrate of that base. Sometimes the attraction between the 

1 Phil. Mag. July, 1839. 



HYDROGEN. 119 

water and the second body is so great that the compound's not decomposable 
by any heat that can be applied ; the hydrates of potassa and soda, and of 
phosphoric acid, furnish examples. Oil of vitriol is a hydrate of sulphuric 
acid, from which the water cannot be thus separated. 

Water very frequently combines with saline substances in a less intimate 
manner than that above described, constituting what is called water of crys- 
tallization, from its connexion with the geometrical figure of the salt. In 
this case it is easily driven off by the application of heat. 

Lastly, the solvent properties of water far exceed those of any other liquid 
known. Among salts, a very large proportion are soluble to a greater or 
less extent, the solubility usually increasing with the temperature, so that a 
hot saturated solution deposits crystals on cooling. There are a few excep- 
tions to this law, one of the most remarkable of which is common salt, the 
solubility of which is nearly the same at all temperatures ; the hydrate and 
certain organic salts of lime, also, dissolve more freely in cold than in hot 
water. 

Water dissolves gases, but in very unequal quantities ; some, as hydrogen, 
oxygen, and atmospheric air, are but little acted upon; others, as ammonia 
and hydrochloric acid, are absorbed to an enormous extent ; and between 
these extremes there are various intermediate degrees. Generally, the colder 
the water, the more gas does it dissolve ; a boiling heat disengages the whole, 
if the gas be not very soluble. 

When water is heated in a strong vessel to a temperature above that of 
the ordinary boiling-point, its solvent powers are still further increased. 
Dr. Turner inclosed in the upper part of a high-pressure steam-boiler, worked 
at 300° (1-49°C), pieces of plate and crown glass. At the expiration of four 
months the glass was found completely corroded by the action of the water ; 
what remained was a white mass of silica, destitute of alkali, while stalac- 
tites of siliceous matter, above an inch in length, depended from the little 
wire cage which inclosed the glass. This experiment tends to illustrate the 
changes which may be produced by the action of water at a high tempe- 
rature in the interior of the earth upon felspathic and other rocks. Some- 
thing of the sort is manifest in the Geyser springs of Iceland, which deposit 
siliceous sinter. 1 

Binoxide of hydrogen, sometimes called oxygenated water, is an exceedingly 
interesting substance, but unfortunately very difficult of preparation. It is 
formed by dissolving the binoxide of barium in dilute hydrochloric acid, 
carefully cooled by ice, and then precipitating the baryta by sulphuric acid ; 
the excess of oxygen of the binoxide, instead of being disengaged as gas, 
unites with a portion of the water, and converts it into binoxide of hydrogen. 
This treatment is repeated with the same solution and fresh portions of the 
binoxide of barium until a considerable quantity of the latter has been con- 
sumed, and a corresponding amount of binoxide of hydrogen formed. The 
liquid yet contains hydrochloric acid, to get rid of which it is treated in suc- 
cession with sulphate of silver and baryta-water. The whole process re- 
quires the utmost care and attention. The binoxide of barium itself is pre- 
pared by exposing pure baryta, contained in a red-hot porcelain tube, to a 
stream of oxygen. The solution of binoxide of hydrogen may be concen- 
trated under the air-pump receiver until it acquires the specific gravity of 
1-45. In this state it presents the aspect of a colourless, transparent, ino- 
dorous liquid, possessing remarkable bleaching powers. It is very prone to 
decomposition ; the least elevation of temperature causes effervescence, due 
to the escape of oxygen gas ; near 212° (100°C) it is decomposed with ex. 

4 Phil. Mag. Oct. 1834. 



120 



NITROGEN. 



Fig. 90. 




plosive violence. Binoxide of hydrogen contains exactly twice as much 
>xygen as water, or 1G parts to 1 part of hydrogen. 

NITROGEN. 

Nitrogen 5 constitutes about four-fifths of the atmosphere, and enters into 
a great variety of combinations. It may be prepared for the purpose of expe- 
riment by several methods. One of the simplest of these is to burn out the 
oxygen from a confined portion of air, by phosphorus, or by a jet of hy- 
drogen. 

A small porcelain capsule is floated on the water of the pneumatic trough, 
and a piece of phosphorus placed in it and set on fire. 
(Fig. 90.) A bell-jar is then inverted over the whole, 
and suffered to rest on the shelf of the trough, so as 
to project a little over its edge. At first, the heat 
causes expansion of the air of the jar, and a few bub- 
bles are expelled, after which the level of the water 
rises considerably. When the phosphorus becomes 
extinguished by exhaustion of the oxygen, and time 
has been given for the subsidence of the cloud of finely- 
divided, snow-like phosphoric acid, which floats in the 
residual gas, the nitrogen may be decanted into ano- 
ther vessel, and its properties examined. 

Prepared by the foregoing process, nitrogen is con- 
taminated by a little vapour of phosphorus, which 
communicates its peculiar odour. A preferable me- 
thod is to fill a porcelain tube with turnings of copper, 
or, still better, with the spongy metal obtained by reducing the oxide by 
hydrogen ; to heat this tube to redness, and then pass through it a stream 
of atmospheric air, the oxygen of which is entirely removed during its pro- 
gress by the heated copper. 

If chlorine gas be passed into solution of ammonia, the latter substance, 
which is a compound of nitrogen with hydrogen, is decomposed ; the chlo- 
rine combines with the hydrogen, and the nitrogen is set free with efferves- 
cence. In this manner very pure nitrogen can be obtained. In making this 
experiment, it is necessary to stop short of saturating or decomposing the 
whole of the ammonia, otherwise there will be great risk of accident from 
the formation of an exceedingly dangerous explosive compound formed by 
the contact of chlorine with an ammoniacal salt. 

Nitrogen is destitute of colour, taste, and smell ; it is a little lighter than 
air, its density being, according to Dumas, 0-972. 100 cubic inches, at 60° 
(15°-5C), and 30 inches barometer, will therefore weigh 30-14 grains. Nitro- 
gen is incapable of sustaining combustion or animal existence, although, like 
hydrogen, it has no positive poisonous properties ; neither is it soluble to 
any notable extent in water or in caustic alkali ; it is, in fact, best charac- 
terized by negative properties. 

The exact composition of the atmosphere has repeatedly been made the 
subject of experimental research. Besides nitrogen and oxygen, the air 
contains a little carbonic acid, a very variable proportion of aqueous vapour, 
a trace of ammonia, and, perhaps, a little carburetted hydrogen. The oxygen 
and nitrogen are in a state of mixture, not of combination, yet their ratio 
is always uniform. Air has been brought from lofty Alpine heights, and 
compared with that from the plains of Egypt; it has been brought from an 
elevation of 21,000 feet by the aid of a balloon ; it has been collected and 
examined in London and Paris, and many other districts ; still the propor- 



1 i. e. Generator of nitre; also called azote, from a, privative, and £u>^ life. 



NITROGEN. 



121 



tions of oxygen and nitrogen remain unaltered, the diffusive energy of the 
gases being adequate to maintain this perfect uniformity of mixture. The 
carbonic acid, on the contrary, being much influenced by local causes, varies 
considerably. In the following table the proportion of oxygen and nitrogen 
are given on the authority of M. Dumas, and the carbonic acid on that of 
De Saussure ; the ammonia, the discovery of which is due to Liebig, is too 
small in quantity for direct estimation. 



Composition of the Atmosphere. 
By weight. 

Nitrogen 77 parts 

Oxygen 23 " 



By measure. 
.. 79-19 
.. 20-81 



Fig. 91. 



100 100-00 

Carbonic acid, from 3-7 measures to 6-2 measures, in 10,000 measures of 
air. 

Aqueous vapour variable, depending much upon the temperature. 

Ammonia, a trace. 

100 cubic inches of pure and dry air weigh, according to Dr. Prout, 
31-0117 grains; the temperature being 60° F. (15°-5C) and the baro- 
meter standing at 30 inches. 

The analysis of air is very well effected by passing it 
over finely-divided copper contained in a tube of hard glass, 
3arefully weighed, and then heated to redness ; the ni- 
trogen is suffered to flow into an exhausted glass globe, 
also previously weighed. The increase of weight after 
the experiment gives the information sought. 

An easier, but less accurate method, consists in intro- 
ducing into a graduated tube, standing over water (fig. 91), 
a known quantity of the air to be examined, and then 
passing into the latter a stick of phosphorus affixed to 
the end of a wire. The whole is left about twenty-four 
hours, during which the oxygen is slowly but completely 
absorbed, after which the phosphorus is withdrawn and the 
residual gas read off. 

Professor Liebig has lately proposed to use an alkaline 
solution of pyro-gallic acid, (a substance which will be 
described in the department of organic chemistry,) for the 
absorption of oxygen. The absorptive power of such a 
solution, which turns deep black on coming in contact with 
the oxygen, is very considerable. Liebig's method combines great accuracy 
with unusual rapidity and facility of execution. 

Another plan is to mix the air with hydrogen and pass an electric spark ; 
after the explosion the volume of gas is read off and compared with that of 
the air employed. Since the analysis of gaseous bodies by explosion is an 
operation of great importance in practical chemistry, it may be worth while 
describing the process in detail, as it is applicable, with certain obvious 
variations, to a number of analogous cases. 

A convenient form of apparatus for the purpose is the siphon eudiometer 
of Dr. Ure ; this consists of a stout glass tube, having an internal diameter 
i>f about one-third of an inch, closed at one end, and bent into the form 
represented in the drawing. (Fig. 92.) Two pieces of platinum wire, 
melted into the glass near the closed extremity, serve to give passage to the 
spark. The closed limb is carefully graduated. When required for use 5 the 




122 



N I T R OGEN 



instrument is filled with mercury and inverted into a 
vessel of the same fluid. A quantity of the air to be 
examined is then introduced, the manipulation being 
precisely the same as with experiments over water ; 
the open end is stopped with a finger, and the air 
transferred to the closed extremity. The instrument 
is next held upright, and after the level of the mer- 
cury has been made equal on both sides by displacing 
a portion from the open limb by thrusting down a 
piece of stick, the volume of air is read off. This 
done, the open part of the tube is again filled up with 
mercury, closed with the finger, inverted into the 
liquid metal, and a quantity of pure hydrogen intro- 
duced, equal, as nearly as can be guessed, to about 
half the volume of the air. The eudiometer is once 
more brought into an erect position, the level of the 
mercury equalized, and the volume again read off; 
the quantity of hydrogen added is thus accurately 
ascertained. All is now ready for the explosion ; the 
instrument is held in the way represented, the open 
end being firmly closed by the thumb, while the knuckle of the fore-finger 
touches the nearer platinum wire ; the spark is then passed by the aid of a 
charged jar or a good electrophorus, and explosion ensues. The air con- 
fined by the thumb in the open part of the tube acts as a spring and mode- 
rates the explosive effect. Nothing now remains but to equalize the level 
of the mercui-y by pouring a little more into the instrument, and then to 
read off the volume for the last time. 

What is required to be known from this experiment is the diminution the 
mixture suffers by explosion ; for since the hydrogen is in excess, and since 
that substance unites with oxygen in the proportion by measure of two to 
one, one-third part of that diminution must be due to the oxygen contained 
in the air introduced. As the amount of the latter is known, the proportion 
of oxygen it contains thus admits of determination. The case supposed 
will render this clear. 




Air introduced 100 measures. 

Air and hydrogen 150 

Volume after explosion 87 



Diminution 63 

63 
3 



!1 ; oxygen in the hundred measures. 



The working pupil will do well to acquire dexterity in the use of this val- 
uable instrument, by practising the transference of gas or liquid from the 
one limb to the other, &c. In the analysis of combustible gases by explo- 
sion with oxygen, solution of caustic potassa is often required to be intro- 
duced into the closed part. 



Compounds of Nitrogen and Oxygen. 

There are not less than five distinct compounds of nitrogen and oxygen, 
thus named and constituted : — 



NITROGEN. 



123 



Composition hy weight . 



Oxygen. 



16 
24 
32 

40 



Nitrogen. 

Protoxide of nitrogen 1 14 ... 

Binoxide of nitrogen 2 14 ... 

Nitrous acid 14 ... 

Hyponitric acid 3 14 ... 

Nitric acid 14 ... 

Nitric or Azotic Acid. — In certain parts of India, and also in other hot dry 
climates where rain is rare, the surface of the soil is occasionally covered 
by a saline efflorescence, like that sometimes apparent on newly-plastered 
walls ; this substance collected, dissolved in hot water, the solution filtered 
and made to crystallize, furnishes the highly important salt known in com- 
merce as nitre or saltpetre; it is a compound of nitric acid and potassa. 
To obtain liquid nitric acid, equal weights of powdered nitre and oil of 
vitriol are introduced into a glass retort, and heat applied by means of an 
Argand gas-lamp or charcoal chauffer. A flask, cooled by a wet cloth, is 
adapted to the retort, to serve for a receiver. No luting of any kind must 
be used. 

As the distillation advances, the red fumes which first arise disappear, but 
towards the end of the process again become manifest. When this happens, 
and very little liquid passes over, while the greater part of the saline matter 
of the retort is in a state of tranquil fusion, the operation may be stopped ; 
and when the retort is quite cold, water may be introduced to dissolve out 
the bisulphate of potassa. The reaction is thus explained. 

Nitre | S™?^ 1 - -^-Liquid nitric acid. 



Oil of vitriol 



Potassa 



Water 
Sulphuric acid 




Bisulphate of potassa. 



In the manufacture of nitric acid on the large scale, the glass retort is 
replaced by a cast-iron cylinder, and the receiver by a series of earthen con- 
densing vessels connected by tubes. (Fig. 93.) Nitrate of soda, found native 
n Peru, is often substituted for nitrate of potassa. 

Fig. 93. 




Liquid nitric acid so obtained has a specific gravity of 1-5 to 1-52 ; it has a 
^ >lden yellow colour, which is due to nitrous or hyponitric acid held in solu- 
tion, and which, when the acid is diluted with water, gives rise by its decom- 
position to a disengagement of nitric oxide. It is exceedingly corrosive, 
staining the skin deep yellow, and causing total disorganization, Poured 
upon red-hot powdered charcoal, it causes brilliant combustion; and when 
added to warm oil of turpentine, acts upon that substance so energetically 
as to set it on fire. 



1 Otherwise called nitrous oxide. 

3 Called hy Professor Graham peroxide of nitrogen. 



2 Otherwise called nitric oxide. 



124 NITROGEN. 

Pure liquid nitric acid, in its most concentrated form, is obtained by mix 
ing the above with about an equal quantity of oil of vitriol, re-distilling, 
collecting apart the first portion wh\ch comes over, and exposing it in a 
vessel slightly warmed, and sheltered from the light, to a current of dry 
air, made to bubble through it, "which completely removes the nitrous acid. 
In this state the product is as colourless as water; it has the sp. gr. 1-517 
at 60° (15° -5C), boils at 184° (84° -5C), and consists of 54 parts real acid, 
and 9 parts water. Although nitric acid in a more dilute form acts very 
violently upon many metals, and upon organic substances generally, this is 
not the case with the compound in question ; even at a boiling heat it re- 
fuses to attack iron or tin, and its mode of action on lignin, starch, and 
similar substances, is quite peculiar, and very much less energetic than that 
of an acid containing more water. 

A second definite compound of real nitric acid and water exists, containing 
54 parts of the former to 36 parts of the latter. Its sp. gr. at 60° (15° -5C) 
is 1-424, and it boils at 250° (121 °C). An acid weaker than this is concen- 
trated to this point by evaporation ; and one stronger, reduced to the same 
amount by loss of nitric acid and water in the form of the first hydrate. 1 

Absolute nitric acid, in the separate state, was unknown up to 1849, when 
M. Deville succeeded in obtaining this remarkable substance by exposing 
nitrate of silver, which is a combination of nitric acid, silver, and oxygen, 
to the action of chlorine gas. Chlorine and silver combine, forming chloride 
of silver, which remains in the apparatus, whilst oxygen and anhydrous 
nitric acid separate. The latter is a colourless substance, crystallizing in 
six-sided columns, which fuse at 80° (30°C), and boil between 113° and 
122° (45° and 50°C), when they commence to be decomposed. Anhydrous 
nitric acid has been found to explode sometimes spontaneously. It dissolves 
in water with evolution of much heat, forming hydrated nitric acid. It con- 
sists of 14 parts of nitrogen and 40 parts of oxygen. 

Nitric acid forms with bases a very extensive and important group of salts, 
the nitrates, which are remarkable for all being soluble in water. The 
hydrated acid is of great use in the laboratory, and also in many branches 
of industry. 

The acid prepared in the way described is apt to contain traces of chlo- 
rine from common salt in the nitre, and sometimes of sulphate from acci- 
dental splashing of the pasty mass in the retort. To discover these impuri- 
ties, a portion is diluted with four or five times its bulk of distilled water, 
and divided between two glasses. Solution of nitrate of silver is dropped 
into the one, and solution of nitrate of baryta into the other ; if no change 
ensue in either case, the acid is free from the impurities mentioned. 

Nitric acid has been formed in small quantity by a very curious process, 
namely, by passing a series of electric sparks through a portion of air, 
water, or an alkaline solution being present. The amount of acid so formed 
after many hours is very minute ; still it is not impossible that powerful 
discharges of atmospheric electricity may sometimes occasion a trifling pro- 
duction of nitric acid in the air. A very minute quantity of nitric acid is 
also produced by the combustion of hydrogen and other substances in the 
atmosphere ; it is also formed by the oxidation of ammonia. 

Nitric acid is not so easily detected in solution in small quantities as many 
other acids. Owing to the solubility of all its compounds, no precipitant can 
be found for this substance. One of the best tests is its power of bleaching 
a solution of indigo in sulphuric acid when boiled with that liquid. The 

1 The two hydrates of nitric acid arc thus expressed by symbols : — NOo, 110 and NOs, 4110. 
Ro compound containing two equivalents of water appears to exist. 



NITROGEN 



125 



absence of chlorine must be ensured in this experiment by means which will 
hereafter be obvious, otherwise the result is equivocal. 

Protoxide of Nitrogen; Nitrous Oxide; (laughing gas.) — When solid nitrate 
of ammonia is heated in a retort or flask, 1 fig. 94, furnished with a perforated 
cork and bent tube, it is resolved into water and nitrous oxide. The nature 
of the decomposition will be understood from the subjoined diagram. 



Nitrate of 
Ammonia 



f Nitrogen 14 
Nitric acid J Oxygen 

54 1 Oxygen 8 

I Oxygen 24 

Ammonia /Nitrogen 14 

17 {Hydrogen 3 

Water 




Protox. nitrogen 22 



Protox. nitrogen 22 
Water 27 



Fig. 94. 



No particular precaution is required in the ope- 
ration, save due regulation of the heat, and the 
avoidance of tumultuous disengagement of the gas. 

Protoxide of nitrogen is a colourless, transparent, 
and almost inodorous gas, of distinctly sweet taste. 
Its specific gravity is 1-525; 100 cubic inches 
weigh 47-29 grains. It supports the combustion 
of a taper or piece of phosphorus with almost as 
much energy as pure oxygen ; it is easily distin- 
guished, however, from that gas by its solubility in 
cold water, which dissolves nearly its own volume ; 
hence it is necessary to use tepid water in the 
pneumatic trough or gas-holder, otherwise great 
loss of gas will ensue. Nitrous oxide has been 
liquefied, but with difficulty ; it requires, at 45° 
(7°-2C) a pressure of 50 atmospheres ; the liquid 
when exposed under the bell-glass of the air-pump 
is rapidly converted into a snow-like solid. When 
mixed with an equal volume of hydrogen, and fired 
by the electric spark in the eudiometer, it explodes 
with violence, and liberates its own measure of nitrogen. Every two vol- 
umes of the gas must consequently contain two volumes of nitrogen and one 
volume of oxygen, the whole being condensed or contracted one-third; a 
constitution resembling that of vapour of water. 3 

The most remarkable feature in this gas is its intoxicating power upon the 
animal system. It may be respired, if quite pure, or merely mixed with 
atmospheric air, for a short time, without danger or inconvenience. The 
effect is very transient, and is not followed by depression. 

Binoxide of Nitrogen ; Nitric Oxide. — Clippings or turnings of copper are 
put into the apparatus employed for preparing hydrogen, 3 together with a 
little water, and nitric acid added by the funnel until brisk effervescence is 
excited. The gas may be collected over cold wa ,er, as it is not sensibly 
soluble. 

The reaction is a simple deoxidation of some of the nitric acid by the 
copper ; the metal is oxidized, and the oxide so formed is dissolved by an- 




1 Florence oil-flasks, which may he purchased at a very trifling sum, constitute exceedingly 
useful vessels for chemical purposes, and often supersede retorts or other expensive appa- 
ratus. They are rendered still more valuahle hy cutting the neck smoothly round with a 
hot iron, softening it in the flame of a good Argand gas-lamp, and then turning over the edge 
so as to form a lip, or border. The neck will then hear a tight-fitting cork without risk of 
b^litliug. 

2 Sec page 113. 8 See page 111. 

11* 



126 NITROGEN. 

other portion of the acid. Nitric acid is very prone to act thus upon certain 
metals. 

The gas obtained in this manner is colourless and transparent ; in contact 
■with air or oxygen gas it produces deep red fumes, which are readily ab- 
sorbed by water; this character is sufficient to distinguish it from all other 
gaseous bodies. A lighted taper plunged into the gas is extinguished; lighted 
phosphorus, however, burns in it with great brilliancy. 

The specific gravity of binoxide of nitrogen is 1-039; 100 cubic inches 
weigh 82-22 grains. It contains equal measures of oxygen and nitrogen 
gases united without condensation. When this gas is passed into a solution 
of protoxide of iron it is absorbed in large quantity, and a deep brown or 
nearly black liquid produced, which seems to be a definite compound of the 
two substances. The compound is again decomposed by boiling. 

Nitrous Acid. — Four measures of binoxide of nitrogen are mixed with one 
measure of oxygen, and the gases, perfectly dry, exposed to a temperature 
of 0° ( — 17° -8C). They condense to a thin mobile green liquid. Its vapour 
is orange-red. 

Nitrous acid is decomposed by water, being converted into nitric acid and 
binoxide of nitrogen. For this reason it cannot be made to unite directly 
with metallic oxides ; nitrite of potassa may, however, be prepared by fusing 
nitrate of potassa, when part of its oxygen is evolved ; and many other salts 
of nitrous acid may be obtained by indirect means. 

Hyponitric Acid. — It has been doubted whether the term acid applied to 
this substance be correct, since it seems to possess the power of forming salts 
only in a very limited degree ; the expression has, notwithstanding, been 
long sanctioned by use. Moreover, a beautiful crystalline lead-salt of this 
substance has been discovered by M. Peligot. It is formed by digesting 
nitrate of lead with metallic lead. 

It is chiefly the vapour of hyponitric acid which forms the deep red fumes 
always produced when binoxide of nitrogen escapes into the air. 

When carefully dried nitrate of lead is exposed to heat in a retort of hard 
glass, it is decomposed ; protoxide of lead remains behind, while the acid is 
resolved into a mixture of oxygen and hyponitric acid. By surrounding the 
receiver with a very powerful freezing mixture, the latter is condensed to 
the liquid form. It is then nearly colourless, but acquires a yellow, and ul- 
timately a red tint, as the temperature rises. At 82° (27°-8C) it boils, 
giving off its well-known red vapour, the intensity of the colour of which is 
greatly augmented by elevation of temperature. 

This substance, like the preceding, is decomposed by water, being resolved 
into binoxide of nitrogen and nitric acid. Its vapour is absorbed by strong 
nitric acid, which thereby acquires a yellow or red tint, passing into green, 
then into blue, and afterwards disappearing altogether on the addition of 
successive portions of water. The deep red fuming acid of commerce, called 
nitrous acid, is simply nitric acid impregnated with hyponitric gas. 1 



Nitrogen appears to combine, under favourable circumstances, with metal3 
AVhcn iron and copper are heated to redness in an atmosphere of ammonia, 
they become brittle and crystalline, but without sensible alteration of weight 
M. Schrotter has shown that in the case of copper, at least, this effect is 

* Much doubt yet hangs over the true nature and relations of these two acids. According 
to M. Peligot, the only product of the union of binoxide of nitrogen and oxygen is hyponitric 
acid, winch in the total absence of water is a white solid crystalline body, fusible at 16° 
( — 8°-9Gy. At common temperatures it is an orange-yellow liquid. The same product is ob- 
tained by heating perfectly dry nitrate of lead. From these experiments it would appear 
♦hat nitrous acid iu a separate state is unknown. Ann. CLiru. et l'hys. 3d series, ii. 58. 



CARBON. 



127 



caused by the formation and subsequent destruction of a nitride, that is, a 
compound of nitrogen with copper. When ammonia is passed over protoxide 
of copper heated to 570° (298°-9C), water is formed, and a soft brown 
powder produced, which when heated farther evolves nitrogen, and leaves 
metallic copper. The same effect is produced by the contact of strong acids. 
A similar compound of chromium^ with nitrogen appears to exist. 

CARBON. 

This substance occurs in a state of purity, and crystallized, in two distinct 
and very dissimilar forms, namely, as diamond, and as graphite or plumbago. 
It constitutes a large proportion of all organic structures, animal and vege- 
table : when these latter are exposed to destructive distillation in close ves- 
sels, a great part of this carbon remains, obstinately retaining some of the 
hydrogen and oxygen, and associated with the earthy and alkaline matter of 
the tissue, giving rise to the many varieties of charcoal, coke, &c. 

The diamond is one of the most remarkable substances known ; long prized 
on account of its brilliancy as an ornamental gem, the discovery of its curi- 
ous chemical nature confers upon it a high degree of scientific interest. 
Several localities in India, the island of Borneo, and more especially Brazil, 
furnish this beautiful substance. It is always distinctly crystallized, often 
quite transparent and colourless, but now and then having a shade of yellow, 
pink, or blue. The origin and true geological position of the diamond are 
unknown ; it is always found embedded in gravel and transported materials, 
whose history cannot be traced. The crystalline form of the diamond is 
that of the regular octahedron or cube, or some figure geometrically con- 
nected with these ; many of the octahedral crystals exhibit a vei*y peculiar 
appearance, arising from the faces being curved or rounded, which gives to 
the crystal an almost spherical figure. 



Kg. 95. 



Fig. 



Fig. 98. 




T"" 




The diamond is infusible and inalterable by a very intense heat, provided 
air be excluded ; but when heated, thus protected, between the poles of a 
strong galvanic battery, it is converted into coke or graphite ; heated to or- 
dinary redness in a vessel of oxygen, it burns with facility, yielding carbonic 
acid gas. 

This is the hardest substance known ; it admits of being split or cleaved 
without difficulty in certain particular directions, but can only be cut or 
abraded by a second portion of the same material ; the powder rubbed off 
in this process serves for polishing the new faces, and is also highly useful 
to the lapidary and seal-engraver. One very curious and useful application 
of the diamond is made by the glazier ; a fragment of this mineral, like a 
bit of flint, or any other hard substance, scratches the surface of glass ; a 
crystal of diamond having the rounded octahedral figure spoken of, held in 
one particular position on the glass, namely, with an edge formed by the 
meeting of two adjacent faces presented to the surface, and then drawn 
along with gentle pressure, causes a deep split or cut, which penetrates to 
a considerable depth into the glass, and determines its fracture with perfect 
certainty. 



128 C A E B X . 

Graphite, or plumbago, appears to consist essentially of pure carbon, al- 
though most specimens contain iron, the quautity of which varies from a 
mere trace up to five per cent. Graphite is a somewhat rare mineral ; the 
finest, and most valuable for pencils, is brought from Borrowdale, in Cum- 
berland, where a kind of irregular vein is found traversing the ancient slate- 
beds of that district. Crystals are not common ; when they occur, they 
have the figure of a short six-sided prism ; — a form bearing no geometric 
relation to that of the diamond. 

Graphite is often formed artificially in certain metallurgic operations; the 
brilliant scales which sometimes separate from melted cast iron on cooling, 
called by the workmen "kish," consist of graphite. 

Lampblack, the soot produced by the imperfect combustion of oil or resin, 
is the best example that can be given of carbon in its uncrystallized or 
amorphous state. To the same class belong the different kinds of charcoal. 
That prepared from wood, either by distillation in a large iron retort, or by 
the smothered combustion of a pile of fagots partially covered with earth, 
is the most valuable as fuel. Coke, the charcoal of pit-coal, is much more 
impure ; it contains a large quantity of earthy matter, and very often sul- 
phur ; the quality depending very much upon the mode of preparation. 
Charcoal from bones and animal matters in general is a very valuable sub- 
stance, on account of the extraordinary power it possesses of removing 
colouring matters from organic solutions ; it is used for this purpose by the 
sugar-refiners to a very great extent, and also by the manufacturing and 
scientific chemist. 1 The property in question is possessed by all kinds of 
charcoal in a small degree. 

Charcoal made from box, or other dense wood, has a property of con- 
densing into its pores gases and vapours ; of ammoniacal gas it is said to 
absorb not less than ninety times its volume, while of hydrogen it takes up 
less than twice its own bulk, the quantity being apparently connected with 
the property in the gas of suffering liquefaction. This effect, as well as 
that of the decolorizing power, no doubt depends in some way upon the 
same peculiar action of surface so remarkable in the case of platinum in a 
mixture of o sygen and hydrogen. 3 

Compounds of Carbon and Oxygen. 
There are two direct inorganic compounds of carbon and oxygen, called 
carbonic oxide and carbonic acid ; their composition may be thus stated: — 

Composition by weight. 



Carbon. Oxygen. 

Carbonic oxide 6 8 

Carbonic acid 6 16 

1 It removes from solution in water the vegetable bases, bitter principles and astringent 
substances, when emploj'ed in excess, requiring from twice to twenty times their weight for 
total precipitation. A solution of iodine in water, or iodide of potassium, is quickly de- 
prived of colour. Metallic salts dissolved in water or diluted alcohol are precipitated, though 
not entirely, requiring about thirty times their weigbt of animal charcoal. Arseuious aci ! 
i> totally carried out of solution. In these cases it acts in three different ways: the salt is 
absorbed unaltered; the oxide in the salt may be reduced; or, the salts precipitated iu a 
basic condition, the solution showing an acid reaction as soon as the carbon besrins to act. It 
is in this last ca.se especially that traces of the bases can be detected, the acid set free pre- 
venting their total precipitation. The precipitation may hence he prevented by adding an 
excess of acid, and the bases after precipitation may ho dissolved out by boiling vim an acid 
solution. — "Warrington, Mem. Chim. Soc. 1S45; Garrod, Pharm. Journ. 1845 ; Weppen, Ann. 
de Chim. 1845. — It. B. 

3 Carbon is a combustible nniting with oxygen and producing carbonic acid. Its different 
forms exhibit much difference in this respect; in the very porous condition of charcoal it 
burns readily, while in its most dense form, the diamond, it requires a bright red heat and 
pure oxygen. In the form of charcoal it conducts heat slowly and electricity readily. Car- 
bon is Insoluble in water and not liable to be affected by air and moisture. It retards putre- 
faction.— It. B. 



CARBON. 



129 



Carbonic Acid is always produced when charcoal burns in air or in oxygen 
gas; it is most conveniently obtained, however, for study, by decomposing 
a carbonate with one of the stronger acids. For this purpose, the apparatus 
for generating hydrogen may be again employed ; fragments of marble are 
put into the bottle, with enough water to cover the extremity of the funnel- 
tube, and hydrochloric or nitric acid added by the latter, until the gas is 
freely disengaged. Chalk-powder and dilute sulphuric acid may be used 
instead. The gas may be collected over water, although with some loss ; or 

Fig. 99. 




very conveniently, by displacement, if it be required dry, as shown in fig. 
99. The long drying-tube is filled with fragments of chloride of calcium, 
and the heavy gas is conducted to the bottom of the vessel in which it is to 
be received, the mouth of the latter being lightly closed. 1 

Carbonic acid gas is colourless ; it has an agreeable pungent taste and 
odour, but cannot be respired for a moment without insensibility following. 
Its specific gravity is 1-524, 3 100 cubic inches weighing 47-26 grains. 

This gas is very hurtful to animal life, even when largely diluted with air; 
it acts as a narcotic poison. Hence the danger arising from imperfect ven- 
tilation, the use of fire-places and stoves of all kinds unprovided with proper 
chimneys, and the crowding together of many individuals in houses and 
ships without efficient means for renewing the air ; for carbonic acid is con- 
stantly disengaged during the process of respiration, which, as we have seen, 
(page 108,) is nothing but a process of slow combustion. This gas is some- 
times emitted in large quantity from the earth in volcanic districts, and it is 
constantly generated where organic matter is in the act of undergoing fer- 
mentive decomposition. The fatal "after-damp" of the coal-mines contains 
a large proportion of carbonic acid. 

1 In connecting tube-apparatus for conveying gases or cold liquids, not corrosive, litt'.u 
tubes of caoutchouc about an inch long, are in- 
expressibly useful. These are made by bending 
a piece of sheet India-rubber, a. fig. 100, loosely 
round a glass tube or rod, o, and cutting off the 
superfluous portion -with sharp scissors. The 
fresh-cut edges of the caoutchouc, pressed strongly 
together, cohere completely, provided they have 
not been soiled by touching with the fingers, and 
the tube is perfect. The connectors are secured 
by two or three turns of tliin silk cord. The 
glass tubes are sold by weight, and are easily 
bent in the flame of a spirit-lamp, and, when 
necessary, cut by scratching with a file, and 
breaking asunder. 

3 MM. Dulong and Berzelius. 



Fig. 100. 




130 CARBON. 

A lighted taper plunged into carbonic acid is instantly extinguished, even 
to the red-hot snuff. When diluted with three times its volume of air, it 
still has the power of extinguishing a light. The gas is easily known from 
nitrogen, which is also incapable of supporting combustion, by its rapid 
absorption by caustic alkali or by lime-water ; the turbidity communicated 
to the latter from the production of insoluble carbonate of lime is very 
characteristic. 

Cold water dissolves about its own volume of carbonic acid, whatever be 
the density of the gas with which it is in contact ; the solution temporarily 
reddens litmus paper. In common soda-water, and also in effervescent 
wines, examples may be seen of this solubility of the gas. Even boiling 
water absorbs a perceptible quantity. 

Some of the interesting phenomena attending the liquefaction of carbonic 
acid have been already described ; it requires for the purpose a pressure of 
between 27 and 28 atmospheres at 32° (0°C), according to Mr. Addams. 
The liquefied acid is colourless and limpid, lighter than water, and four 
times more expansible than air; it mixes in all proportions with ether, 
alcohol, naphtha, oil of turpentine, and bisulphide of carbon, and is insoluble 
in water and fat oils. It is probably destitute when in this condition of all 
properties of an acid. 1 

Carbonic acid exists, as already mentioned, in the air ; relatively, its quan- 
tity is but small, but absolutely, taking into account the vast extent of the 
atmosphere, it is very great, and fully adequate to the purpose for which it 
is designed, namely, to supply to plants their carbon, these latter having 
the power, by the aid of their green leaves, of decomposing carbonic acid, 
retaining the carbon, and expelling the oxygen. The presence of light is 
essential to this extraordinary effect, but of the manner of its execution we 
are yet ignorant. 

The carbonates form a very large and important group of salts, some of 
which occur in nature in great quantities, as the carbonates of lime and mag- 
nesia. 

Carbonic Oxide. — When carbonic acid is passed over red-hot charcoal or 
metallic iron, one-half of its oxygen is removed, and it becomes converted 
into carbonic oxide. A very good method of preparing this gas is to intro- 
duce into a flask fitted with a bent tube some crystallized oxalic acid, or salt 
of sorrel, and pour upon it five or six times as much strong oil of vitriol. 
On heating the mixture the organic acid is resolved into water, carbonic acid, 
and carbonic oxide ; by passing the gases through a strong solution of caus- 
tic potassa, the first is withdrawn by absorption, while the second remains 
unchanged. Another, and it may be preferable method, is to heat finely- 
powdered yellow ferrocyanide of potassium with eight or ten times its weight 
of concentrated sulphuric acid. The salt is entirely decomposed, yielding a 
most copious supply of perfectly pure carbonic oxide gas, which may be col- 
lected over water in the usual manner. 2 

Carbonic oxide is a combustible gas ; it burns with a beautiful pale blue 
flame, generating carbonic acid. It has never been liquefied. It is colour- 
less, has very little odour, and is extremely poisonous, even worse than 
carbonic acid. Mixed with oxygen, it explodes by the electric spark, but 

1 When relieved of pressure it immediately boils, and seven parts out of' eight assume the 
g~.seous state, the rest becoming solid at — 9U° (U7 a 7C) (Mitchell). Solid carhouic acid mixed 
with other produces in vacuo a very intense cold ( — 105° [109°-4C] Faraday), capable of 
.solidifying many gases when aided by pressure. Liquid carhouic acid immersed iu this mix- 
ture becomes a solid so clear and transparent that its condition cannot be detected until a 
portion asain becomes liquid. — R. B. 

* See a^paner by the author, in Memoirs of Chem. Soc. of London, i. 251. 1 eq. crystal* 
li/.ed ferrocyanide of potassium, and C eq. oil of vitriol, yield 6 eq. carbonic oxide, 2 eq. sul 
phate of potassa. 3 eq. sulphate of ammonia, and 1 eq. protosulpliate of iron. 



SULPHUR. 



131 



with some difficulty. Its specific gravity is 0-973 ; 100 cubic inches weigh 
30-21 grains. 

The relation by volume of these oxides of carbon may thus be mn.de in- 
telligible : — carbonic acid contains its own volume of oxygen, that gas suffer- 
ing no change of bulk by its conversion. One measure of carbonic oxide 
mixed with half a measure of oxygen and exploded, yields one measure of 
carbonic acid; hence carbonic oxide contains half its volume of oxygen. 

Carbonic oxide unites with chlorine under the influence of light, forming 
a pungent, suffocating compound, possessing acid properties, called phosgene 
gas, or chloro-carbonic acid. It is made by mixing equal volumes of car- 
bonic oxide and chlorine, both perfectly dry, and exposing the mixture to 
sunshine ; the gases unite quietly, the colour disappears, and the volume 
becomes reduced to one-half. It is decomposed by water. 



SULPHUR. 

This is an elementary body of great importance and interest. Sulphur 
is often found in a free state in connection with deposits of gypsum and rock- 
salt ; its occurrence in volcanic districts is probably accidental. Sicily fur- 
nishes a large proportion of the sulphur employed in Europe. In a state of 
combination with iron and other metals, and as sulphuric acid, united to 
lime and magnesia, it is also abundant. 

Pure sulphur is a pale yellow brittle solid, of well-known appearance. It 
melts when heated, and distils over unaltered, if air be excluded. The crys- 
tals of sulphur exhibit two distinct and incompatible forms, namely, an oc- 
tahedron with rhombic base (fig. 101), which is the figure of native sulphur, 
and that assumed when sulphur separates from solution at common tempe- 
ratures, as when a solution of sulphur in bisulphide of carbon is exposed to 
slow evaporation in the air; and a lengthened prism (fig. 103), having no 
relation to the preceding ; this happens when a mass of sulphur is melted, 
and, after partial cooling, the crust at the surface broken, and the fluid por 
tion poured out. Fig. 102 shows the result of such an experiment. 



Fig. 101. 



Ti S . 102. 



Fig. 103. 






The specific gravity of sulphur varies according to the form in which it is 
crystallized. The octahedral variety has a specific gravity 2-045 ; the pris- 
matic variety a specific gravity 1-982. 

Sulphur melts at 232° (111°-1C) ; at this temperature it is of the colour 
of amber, and thin and fluid as water; when farther heated, it begins to 
thicken, and to acquire a deeper colour; and between 430° (221°C) and 180° 
(219°C), it is so tenacious that the vessel in which it is contained may be 
inverted for a moment without the loss of its contents. If in this state it be 
poured into water, it retains for many hours its remarkable soft and flexible 
condition, which should be looked upon as the amorphous state of sulphur. 
After a while it again becomes brittle and crystalline. From the tempera- 
ture last mentioned to the boiling-point, about 792° (400°C) > sulphur ag;uu 



132 SULPHUR. 

becomes thin and liquid. In the preparation of commercial flowers of sul- 
phur, the vapour is conducted into a large cold chamber, where it condenses 
in minute crystals. The specific gravity of sulphur-vapour is 6-654. 

Sulphur is insoluble in water and alcohol ; oil of turpentine and the fat 
oils dissolve it, but the best substance for the purpose is bisulphide of car- 
bon. In its chemical relations sulphur bears great resemblance to oxygen ; 
to very many oxides there are corresponding sulphides, and these sulphides 
often unite among themselves, forming crystallizable compounds analogous 
to salts. 

Compounds of Sulphur and Oxygen. 

Composition by weight. 

Sulphur. Oxygen. 

Sulphurous acid 16 16 

Sulphuric acid 1 16 24 

Hyposulphurous acid 32 16 

Hyposulphuric acid 32 40 

Sulphuretted hyposulphuric acid 48 40 

Bisulphuretted hyposulphuric acid a 04 40 

Trisulphuretted hyposulphuric acid 80 40 

Sulphurous Acid. — This is the only product of the combustion of sulphur 
in dry air or oxygen gas. It is most conveniently prepared by heating oil 
of vitriol with metallic mercury or copper clippings; a portion of the acid 
is decomposed, one-third of its oxygen being transferred to the metal, while 
the sulphuric acid becomes sulphurous. Sulphurous acid thus obtained is a 
colourless gas, having the peculiar suffocating odour of burning brimstone ; 
it instantly extinguishes flame, and is quite irrespirable. Its density is 2-21, 
100 cubic inches weighing 68-69 grains. At 0° ( — 17 0, 8C), under the pres- 
sure of the atmosphere, this gas condenses to a colourless, limpid liquid, 
very expansible by heat. Cold water dissolves more than thirty times its 
volume of sulphurous acid. The solution may be kept unchanged so long 
as air is excluded, but access of oxygen gradually converts the sulphurous 
into sulphuric acid, in the presence of water, although the dry gases may 
remain in contact for any length of time without change. When sulphurous 
acid and aqueous vapour are passed into a vessel cooled to below 17° or 21° 
( — 6° or — 8°C), a crystalline body forms, which contains about 24-2 acid to 
75-8 water. 

One volume of siilphurous acid gas contains one volume of oxygen, and 
^th of a volume of sulphur- vapour, condensed into one volume. 

Gases which, like the present, are freely soluble in water, must be col- 
lected by displacement, or by the use of the mercurial pneumatic trough. 

1 The terminations ous and ?'c, applied to acids, signify degrees of oxidation, the latter being 
the highest; acids ending in ous form salts the names of which are made to end in He. and 
those in ic terminate in ale, as sulphurous acid, sulphite of soda, stdjjJniric acid, suljiliate of 
soda. 

2 The more advanced student will he glad to see these stated in equivalents by the usr^ of 
symbols, hereafter to be explained, their relations becoming thereby much more evident. The 
numbers given are really the equivalent numbers, but are intended only to show the pro- 
portions of sulphur and oxygen, without any reference to other bodies. The following are 
the quantities required to saturate one equivalent of a base: 

Sulphurous acid SOa 

Sulphuric acid SO3 

Ilyposulphurcms acid SaOj 

Hyposulphuric acid, Dithionic acid S-iOd 

Sulphuretted hyposulphuric acid, Trithionic acid S3O5 

Bisulphuretted hyposulphuric acid, TetrcUTrionic acid S4O2 

Trisulphuretled hyposulphuric acid, I'entathiouic acid SaOs 



SULPHUR. 133 

The manipulation with the latter is exactly the same in principle as "with the 
ordinary "water-trough, but rather more troublesome, from the great density 
of the mercury, and its opacity. The whole apparatus is on a much 
smaller scale. The trough is best constructed of hard, sound wood, and so 
contrived as to economise as much as possible the expensive fluid it is to 
contain. 

Sulphurous acid has bleaching properties ; it is used in the arts for bleach- 
ing woollen goods and straw-plait. A piece of blue litmus-paper plunged 
into the moist gas is first reddened and then slowly bleached. 

The salts of sulphurous acid are not of much importance ; those of the 
alkalis are soluble and crystallizable ; they are easily formed by direct com- 
bination. Sulphites of baryta, strontia, and lime, are insoluble in water, 
but soluble in hydrochloric acid. The strong acids decompose them ; nitric 
acid converts them into sulphates. 

Sulphuric Acid. — Hydrated sulphuric acid has been known since the 
fifteenth century. There are two distinct processes by which it is at the 
present time prepared, namely, by the distillation of green sulphate of iron, 
and by the oxidation of sulphurous acid by nitrous acid. 

The first process is still carried on in some parts of Germany, especially 
in the neighbourhood of Nordhausen in Prussia ; the sulphate of iron, derived 
from the oxidation of iron pyrites, is deprived by heat of the greater part 
of its water of crystallization, and subjected to a high red heat in earthen 
retorts, to which receivers are fitted as soon as the acid begins to distil over. 
A part gets decomposed by the very high temperature ; the remainder is 
driven off in vapour, which is condensed by the cold vessel. The product is 
a brown oily liquid, of about 1-9 specific gravity, fuming in the air, and very 
corrosive. It is chiefly made for the purpose of dissolving indigo. 

The second method, which is perhaps, with the single exception mentioned, 
always followed as the more economical, depends upon the fact, that, when 
sulphurous acid, hyponitric acid, and water are present in certain propor- 
tions, the sulphurous acid becomes oxidized at the expense of the hyponitric 
acid, which by the loss of one-half of its oxygen sinks to the condition of 
binoxide of nitrogen. The operation is thus conducted : — A large and vei-y 
long chamber is built of sheet-lead supported by timber framing ; on the 
outside, at one extremity, a small furnace or oven is constructed, having a 
wide tube leading into the chamber. In this sulphur is kept burning, the 
flame of which heats a crucible containing a mixture of nitre and oil of 
vitriol. A shallow stratum of water occupies the floor of the chamber, 
and sometimes a jet of steam is also introduced. Lastly, an exit is provided 
at the remote end of the chamber for the spent and useless gases. The 
effect of these arrangements is to cause a constant supply of sulphurous 
acid, atmospheric air, nitric acid vapour, and water in the state of steam, 
to be thrown into the chamber, there to mix and react upon each other. 
The nitric acid immediately gives up a part of its oxygen to the sulphurous 
acid, becoming hyponitric ; it does not remain in this state, however, but 
suffers farther deoxidation until it is reduced to binoxide of nitrogen. That 
substance in contact with free oxygen absorbs a portion of the latter, and 
once more becomes hyponitric acid, which is again destined to undergo de- 
oxidation by a fresh quantity of sulphurous acid. A very small portion of 
hyponitric acid, mixed with atmospheric air and sulphurous acid, may thus 
in time convert an indefinite amount of the latter into sulphuric acid, by 
acting as a kind of carrier between the oxygen of the air and the sulphurous 
acid. The presence of water is essential to this reaction. 

We may represent the change by the diagram on the succeeding page : — 
12 



134 SULPIIUR 

r Nitrogen 14 ^_ „ Binoxide of nitrogen 30 

llyponitric acid 46 -| Oxygen 16 - 
I Oxygen 16^ 
/Sulphur 32 



Sulphurous acid 64 



( Oxygen 




Water 18 ^ w Hydrated sulphuric acid 98 

Such is the simplest view that can be taken of the production of sulphuric 
acid in the leaden chamber, but it is too much to affirm that it is strictly 
true ; it may be more complex. When a little water is put at the bottom of 
a large glass globe, so as to maintain a certain degree of humidity in the 
air within, and sulphurous and hyponitric acids are introduced by separate 
tubes, symptoms of chem cal action become immediately evident, and after 
a little time a white crystalline matter is observed to condense on the sides 
of the vessel. This substance appears to be a compound of sulphuric acid, 
nitrous acid, and a little water. 1 When thrown into water, it is resolved into 
sulphuric acid, binoxide of nitrogen, and nitric acid. This curious body is 
certainly very often produced in large quantity in the leaden chambers ; but 
that its production is indispensable to the success of the process, and con- 
stant when the operation goes on well, and the hyponitric acid is not in 
excess, may perhaps admit of doubt. 

The water at the bottom of the chamber thus becomes loaded with sul- 
phuric acid ; when a certain degree of strength has been reached, it is drawn 
off and concentrated by evaporation, first in leaden pans, and afterwards in 
stills of platinum, until it attains a density (when cold) of 1-84, or there- 
abouts ; it is then transferred to carboys, or large glass bottles fitted in bas- 
kets, for sale. In Great Britain this manufacture is one of great national 
importance, and is carried on to a vast extent. An inferior kind of acid is 
sometimes made by burning iron pyrites, or poor copper ore, as a substitute 
for Sicilian sulphur; this is chiefly used by the makers for their own con^ 
sumption ; it very frequently contains arsenic. 

The most concentrated sulphuric acid, or oil of vitriol, as it is often called, 
is a definite combination of 40 parts real acid, and 9 parts water. It is a 
colourless, oily liquid, having a specific gravity of about 1-85, of intensely 
acid taste and reaction. Organic matter is rapidly charred and destroyed 
by this substance. At the temperature of — 15° ( — 26°-lC) it freezes; at 
620° (326° -6C) it boils, and may be distilled without decomposition. Oil of 
vitriol has a most energetic attraction for water; it withdraws aqueous 
vapours from the air, and when diluted, great heat is evolved, so that the 
mixture always requires to be made with caution. Oil of vitriol is not the 
only hydrate of sulphuric acid ; three others are known to exist. When the 
fuming oil of vitriol of Nordhausen is exposed to a low temperature, a white 
crystalline substance separates, which is a hydrate containing half as much 
water as the common liquid acid. Then, again, a mixture of 49 parts strong 
liquid acid and 9 parts water, congeals or crystallizes at a temperature above 

1 M. Gaultier de Claubry assigned to this curious substance the composition expressed l.y 
the formula 4IIO, 2NO3+0SO3, and this view has generally been received by recent chemical 
writers. M. de la Provostaye has since shown that a compound, possessing all the essential 
properties of the body in question, may be formed by bringing together, in a scaled glass 
tube, liquid sulphurous acid and liquid hyponitric acid, both free from water. The white 
crystalline solid soon begins to form, and at the expiration of twenty-six hours the reaction 
appears complete. The new product is accompanied by an exceedingly volatile greenish 
liquid having the characters of nitrous acid. The white Bubstance, on analysis, was found 
to contain the elements of two equivalents of sulphuric acid and one of nitrous acid, or 
NO3+2SO3. M. de la Provostaye very ingeniously explains the anomalies in the different 
analyses of the leaden chamber product, by showing that the pure suhstauce forms crystal- 
lizable combinations with different proportions of liquid sulphuric acid. (Ann. Chini. et 
Phys. lxxiii. 362.) 



SULPHUR. 135 

32° (0°C), and remains solid even at 45° (7°-2C). Lastly, when a very 
dilute acid is concentrated by evaporation in vacuo over a surface of oil of 
vitriol, the evaporation stops when the real acid and water bear to each 
other the proportion of 40 to 27. 

"When good Nordhansen oil of vitriol is exposed in a retort to a gentle 
heat, and a receiver cooled by a freezing mixture fitted to it, a volatile 
substance distils over in great abundance, which condenses into beautiful, 
white, silky crystals, resembling those of asbestus ; this bears the name of 
anhydrous sulphuric acid. When put into water it hisses like a hot iron, 
from the violence with which combination occurs ; exposed to the air even 
for a few moments, it liquefies by absorption of moisture, forming common 
liquid sulphuric acid. It forms an exceedingly curious compound with dry 
ammoniacal gas, quite distinct from ordinary sulphate of ammonia, and 
which indeed possesses none of the characters of a sulphate. This interest- 
ing substance may also be obtained by distilling the most concentrated oil 
of vitriol with a sufficient quantity of anhydrous phosphoric acid. 

Sulphuric acid, in all soluble states of combination, may be detected with 
the greatest ease by solution of nitrate of baryta, or chloride of barium. A 
white precipitate is produced, which does not dissolve in nitric acid. 

Hypo sulphurous Acid. — By digesting sulphur with a solution of sulphite 
of potassa or soda, a portion of that substance is dissolved, and the liquid, 
by slow evaporation, furnishes crystals of the new salt. The acid cannot be 
isolated ; when hydrochloric acid is added to a solution of a hyposulphite, 
the acid of the latter is almost instantly resolved into sulphur, which pre- 
cipitates, and into sulphurous acid, easily recognized by its odour. The 
most remarkable feature of the alkaline hyposulphites is their property of 
dissolving certain insoluble salts of silver, as the chloride — a property which 
has lately conferred upon them a considerable share of importance in rela- 
tion to the art of photogenic drawing. 

Hyposulphuric Acid, Dithionic Acid. — This is prepared by suspending 
finery divided binoxide of manganese in water artificially cooled, and then 
transmitting a stream of sulphurous acid gas ; the binoxide becomes pro- 
toxide, half its oxygen converting the sulphurous acid into hyposulphuric. 
The hyposulphate of manganese thus prepared is decomposed by a solution 
of pure l^drate of baryta, and the barytic salt, in turn, by enough sul- 
phuric acid to precipitate the base. The solution of hyposulphuric acid 
may be concentrated by evaporation in vacuo, until it acquires a density of 
1 -347 : pushed farther, it decomposes into sulphuric and sulphurous acids. 
It has no odour, is very sour, and forms soluble salts with baryta, lime, and 
protoxide of lead. 

Sulphuretted hyposulphuric Acid, Trithionic Acid. — A substance accidentally 
formed by M. Langlois, 1 in the preparation of hyposulphite of potassa, by 
gently heating with sulphur a solution of carbonate of potassa, saturated 
with sulphurous acid. The salts bear a great resemblance to those of hypo- 
suiphurous acid, but differ completely in composition, while the acid itself 
is not quite so prone to change. It is obtained by decomposing the potassa 
salt by hydrofluosilicic acid ; it may be concentrated under the receiver of 
the air-pump, but it is gradually decomposed into sulphur, sulphurous and 
sulphuric acids. 

Bisulphurettcd hyposulphuric Acid, Tetraihionic Acid. — This was discovered 
by MM. Fordos and Gelis. 2 When iodine is added to a solution of hyposul- 
j>>itH of soda, a large quantity of that substance is dissolved, and a clear, 
t 'V vless solution obtained, which, besides iodide of sodium, contains a salt 



1 Ann. Chim. et Phys. 3d series, iv. 77. 
8 Hj. 3d series, vi. 4-Ji 



136 SELENIUM. 

of a peculiar acid, richer in sulphur than the preceding. By suitable means, 
the new substance can be eliminated, and obtained in a state of solution. 
It very closely resembles hyposulphuric acid. The same acid is produced by 
the action of sulphurous acid on subchloride of sulphur. 

Trisulphuretted hyposulphuric Acid, Pentathionic Acid. — Another acid of 
sulphur has been announced by M. Wackenroder, who formed it by the 
action of sulphuretted hydrogen on sulphurous acid. It is described as 
colourless and inodorous, of acid and bitter taste, and capable of being con- 
centrated to a considerable extent by cautious evaporation. It contains S 5 5 ; 
under the influence of heat, it is decomposed into sulphur, sulphurous and 
sulphuric acid and sulphuretted hydrogen. The salts of pentathionic acids 
are nearly all soluble. The baryta salt crystallizes from alcohol in square 
prisms. The acid is also formed when hyposulphate of lead is decomposed 
by sulphuretted hydrogen, and when protochloride of sulphur is heated with 
sulphurous acid. 

Sulphurous acid unites, under peculiar circumstances, with chlorine, and 
also with iodine, forming compounds, which have been called chloro- and 
iodo-sulphuric acids. They are decomposed by water. It also combines 
with dry ammoniacal gas, giving rise to a remarkable compound ; and with 
nitric oxide also, in presence of an alkali. 

SELENIUM. 

This is a very rare substance, much resembling sulphur in its chemical 
relations, and found in association with that element in some few localities, 
or replacing it in certain metallic combinations, as in the selenide of lead of 
Clausthal, in the Hartz. 

Selenium is a reddish-brown solid body, somewhat translucent, and having 
an imperfect metallic lustre. Its specific gravit}^ when rapidly cooled after 
fusion, is 4-3. At 212° (100°C), or a little above, it melts, and at 650° 
(343°-3C) boils. It is insoluble in water, and exhales, when heated in the 
air, a peculiar and disagreeable odour, which has been compared to that of 
decaying horseradish. There are three oxides of selenium, two of which 
correspond respectively to sulphurous and sulphuric acids, while the third 
has no known analogue in the sulphur series. 

Composition by weight 



Selenium. Oxygen. 

Oxide of selenium 39-5 8 

Selenious acid 39-5 16 

Selenic acid 39-5 24 

Oxide. — Formed by heating selenium in the air. It is a colourless gas, 
slightly soluble in water, and has the remarkable odour above described. It 
has no acid properties. 

Selenious Acid. — This is obtained by dissolving selenium in nifric acid, and 
evaporating to dryness. It is a white, soluble, deliquescent substanee, of 
distinct acid properties, and may be sublimed without decomposition. Sul- 
phurous acid decomposes it, precipitating the selenium. 

Selenic Acid. — Prepared by fusing nitrate of potassa or soda with selenium, 
precipitating the seleniate so produced by a salt of lead, and then decom- 
posing the compound by sulphuretted hydrogen. The hydrated acid strongly 
resembles oil of vih-iol ; but, when very much concentrated, decomposes, by 
the application of heat, into selenious acid and oxygen. The seleniates bear 
the closest analogy to the sulphates in every particular. 



PHOSPHORUS. 



137 



PHOSPHORUS. 



~~k 



Phosphorus in a state of phosphoric acid is contained in the ancient un- 
etratified rocks, and in the lavas of modern origin. As these disintegrate and 
crumble down into fertile soil, the phosphates pass into the organism of 
plants, and ultimately into the bodies of the animals to which these latter 
serve for food. The earthy phosphates play a very important part in the 
structure of the animal frame, by communicating stiffness and inflexibility 
to the bony skeleton. 

This element was discovered in 1669 by Brandt, of Hamburg, who pre- 
pared it from urine. The following is an outline of the process now adopted. 
Thoroughly calcined bones are reduced to powder, and mixed with two- 
thirds of their weight of sulphuric acid, diluted with a considerable quantity 
of water ; this mixture, after standing some hours, is filtered, and the nearly 
insoluble sulphate of lime washed. The liquid is then evaporated to a 
syrupy consistence, mixed with charcoal powder, and the desiccation com- 
pleted in an iron vessel exposed to a high temperature. When quite dry, 
it is transferred to a stoneware retort, to which a wide bent tube is luted, 
dipping a little way into the water contained in the receiver. A narrow tube 
•serves to give issue to the gases, which are con- 
veyed to a chimney. (Fig. 104.) This manufac- Fig. 104. 
ture is now conducted on a very great scale, the 
consumption of phosphorus, for the apparently 
trifling article of instantaneous light matches, 
being something prodigious. 

Phosphorus, when pure, very much resembles 
in appearance imperfectly bleached wax, and is 
soft and flexible at common temperatures. Its 
density is 1-77, and that of its vapour 4-35, air 
being unity. At 108° (42°-2C) it melts, and at 
550° (287° -7C) boils. It is insoluble in water, 
and is usually kept immersed in that liquid, but 
dissolves in oils, in native naphtha, and especially 
in bisulphide of carbon. When set on fire in 
the air, it burns with a bright flame, generating 
phosphoric acid. Phosphorus is exceedingly in- 
flammable ; it sometimes takes fire by the heat, 
of the hand, and demands great care in its management ; a blow or hard 
rub will very often kindle it. A stick of phosphorus held in the air always 
appears to emit a whitish smoke, which in the dark is luminous. This effect 
is chiefly due to a slow combustion which the phosphorus undergoes by the 
oxj'gen of the air, and upon it depends one of the methods employed for the 
analysis of the atmosphere, as already described. It is singular that the 
slow oxidation of phosphorus may be entirely prevented by the presence of 
a small quantity of olefiant gas, or the vapour of ether, or some essential 
oil ; it may even be distilled in an atmosphere containing vapour of oil of 
turpentine in considerable quantity. Neither does the action go on in pure 
oxygen, at least at the temperature of 60° (15°-5C), which is very remark- 
able ; but if the gas be rarefied, or diluted with nitrogen, hydrogen, or car- 
bonic acid, oxidation is set up. According to the researches of Marchand, 
evaporation of phosphorus causes a luminosity, even when there is no ox ; da- 
tion. 

A very remarkable modification of this element is known by the name of 

amorphous phosphorus. It was discovered by Schrotter, and may be made 

by exposing for fifty hours common phosphorus to a temperature of about 

464° to 482° (240° to 250°C) in an atmosphere which is unable to act chemi- 

12 * 




138 PHOSPHORUS. 

cally upon it. At this temperature it becomes red and opaque, and insoluble 
in bisulphide of carbon, whereby it may be separated from ordinary phos- 
phorus. It may be obtained in compact masses when common phosphorus 
is kept for eight days at a constant high temperature. It is a coherent, 
veil dish-brown, infusible substance, of specific gravity between 2-089 and 
2 106. It does not become luminous in the dark until its temperature is 
raised to about 392° (200°C), nor has it any tendency to combine with the 
oxygen of the air. When heated to 500° (260°C), it is reconverted into 
ordinary phosphorus. 

Compounds of Phosphorus and Oxygen. — These are four in number, and 
have the composition indicated below. 

Composition by weight. 

Phosphorus. Oxygen. 

Oxide of phosphorus 64 8 

Hypophosphorous acid 32 8 

Phosphorous acid 32 24 

Phosphoric acid ' 32 40 

Oxide of Phosphorus. — When phosphorus is melted beneath the surface of 
hot water, and a stream of oxygen gas forced upon it from a bladder, com- 
bustion ensues, and the phosphorus is converted in great part into a brick- 
red powder, which is the substance in question. It is decomposed by heat 
into phosphorus and phosphoric acid. 

Hypophosphorous Acid. — When phosphide of barium is put into hot water, 
that liquid is decomposed, giving rise to phosphoretted hydrogen, phos- 
phoric acid, hypophosphorous acid, and baryta ; the first escapes as gas, and 
the two acids remain in union with the baryta. By filtration the soluble 
hypophosphite is separated from the insoluble phosphate. On adding to the 
liquid the quantity of sulphuric acid necessary to precipitate the base, the 
hypophosphorous acid is obtained in solution. By evaporation it may be 
reduced to a syrupy consistence. 

The acid is very prone to absorb more oxygen, and is therefore a powerful 
deoxidizing agent. All its salts are soluble in water. 

Phosphorous Acid. — Phosphorous acid is formed by the slow combustion 
of phosphorus in the atmosphere ; or by burning that substance by means 
of a very limited supply of air, in which case it is anhydrous, and presents 
the aspect of a white powder. The hydrated acid is more conveniently 
prepared by adding water to the terchloride of phosphorus, when mutual 
decomposition takes place, the oxygen of the water being transferred to the 
phosphorus, generating phosphorous acid, and its hydrogen to the chlorine, 
giving rise to hydrochloric acid. By evaporating the solution to the con- 
sistence of syrup, the hydrochloric acid is expelled, and the residue on 
cooling crystallizes. 

Hydrated phosphorous acid is \ery deliquescent and very prone to attract 
oxygen and pass into phosphoric acid. When heated in a close vessel, it is 
resolved into hydrated phosphoric acid and pure phosphoretted hydrogen gas. 
It is composed of 56 parts real acid and 27 parts Avater. 2 

The phosphites are of little importance. 
• Phosphoric Acid. — When phosphorus is burned under a bell-jar bj' the aid 
of a copious supply of dry air, snow-like anhydrous phosphoric acid is pro- 

1 In symbols — Oxide of phosphorus PaO 

Hypophosphorous acid P O 

Phosphorous acid P O3 

Phosphoric acid P Oa 

Equivalent of phosphorus, o2 

Q Or, 3IIO, PO*. 



OHLOR INE . 



139 



duced in great quantity. This substance exhibits as much attraction for 
-water as anhydrous sulphuric acid ; exposed to the air for a few moments, 
it deliquesces to a liquid, and when thrown into water, combines ■with the 
latter with explosive violence. Once in the state of hydrate, the water 
cannot again be separated. 

When nitric acid of moderate strength is heated in a retort to which a 
receiver is connected, and fragments of phosphorus added singly, taking 
care to suffer the violence of the action to subside between each addition, 
the phosphorus is oxidized to its maximum, and converted into phosphoric 
acid. By distilling off the greater part of the acid, transferring the residue 
In the retort to a platinum vessel, and then cautiously raising the heat to 
redness, the hydrated acid may be obtained pure. This is the glacial phos- 
phoric acid of the Pharmacopoeia. 

A third method consists in taking the acid phosphate of lime produced by 
the action of sulphuric acid on bone-earth, precipitating it with a slight 
excess of carbonate of ammonia, separating by a filter the insoluble lime- 
salt, and then evaporating and igniting in a platinum vessel the mixed 
phosphate and sulphate of ammonia. Hydrated phosphoric acid alone remains 
behind. The acid thus obtained is not remarkable for its purity. One of 
the most advantageous methods of preparing phosphoric acid on the large 
scale in a state of purity, is to burn phosphorus in a stream of dry atmo- 
spheric air, by the aid of a proper apparatus, not difficult to contrive, in 
which the process may be carried on continuously. The anhydrous acid 
obtained may be preserved in that state, or converted into hydrate or glacial 
acid, by the addition of water and subsequent fusion in a platinum vessel. 
The hydrate of phosphoric acid is exceedingly deliquescent, and requires to 
be kept in a closely stopped bottle. It contains 72 parts real acid, and 9 
parts water. 

Phosphoric acid is a powerful acid ; its solution has an intensely sour 
taste, and reddens litmus paper ; it is not poisonous. 

There are few bodies that present a greater degree of interest to tho 
chemist than this substance ; the extraordinary changes 
its compounds undergo by the action of heat, chiefiy Fi S- 105. 

made known to us by the admirable researches of 
Prof. Graham, will be found described in connection 
with the general history of saline compounds. 

CHLORINE. 

This substance is a member of a small natural group 
containing besides iodine, bromine and fluorine. So 
great a degree of resemblance exists between these 
bodies in all their chemical relations, that the history 
of one will almost serve, with a few little alterations, 
for that of the rest. 

Chlorine ' is a very abundant substance ; in common 
salt it exists in combination with sodium. It is most 
easily prepared by pouring strong liquid hydrochloric 
acid upon finely-powdered black oxide of manganese, 
contained in a retc ', or flask, and applying a gentle 
heat; a heavy ye\~ow gas is disengaged, which is the 
substance in question. (Fig. 105.) 

It may be collected over warm water, or by displace- 
ment; the mercurial trough cannot be employed, as 
the chlorine rapidly acts upon the metal, and becomes 
absorbed. 




yXw^/oy , yellowish-green, the name given to it by Sir H. Davy. 




140 CHLORINE. 

The reaction is very easily explained. Hydrochloric acid is a compound 
of chlorine and hydrogen ; when this is mixed with a metallic protoxide, 
double interchange of elements takes place, water and chloride of the metal 
being produced. But when some of the binoxides are substituted, an addi- 
tional effect ensues, namely, the decomposition of a second portion of hydro- 
chloric acid by the oxygen in excess, the hydrogen of which is withdrawn, 
and the chlorine set free. 

Hydrochloric / Chlorine -Chlorine. 

acid \ Hydrogen ^________- — -- Water. 

Binoxide of f 0x yS en ~^~^ 

uinoxiae ot j Manganese ^^ Chloride of manganese. 

manganese { 0xy | en 

Hydrochloric ( Chlorine - 

acid \ Hydrogen ^~~" — -^ Water. 

Chlorine was discovered in 1774, by Scheele, but its nature was long mis- 
understood. It is a yellow gaseous body, of intolerably suffocating proper- 
ties, producing very violent cough and irritation when inhaled even in ex- 
ceedingly small quantity. It is soluble to a considerable extent in water, 
that liquid absorbing at 60° (15° -5C) about twice its volume, and acquiring 
the colour and odour of the gas. When this solution is exposed to light, it 
is slowly changed by decomposition of water into hydrochloric acid, the 
oxygen being at the same time liberated. When moist chlorine gas is 
exposed to a cold of 32° (0°C), yellow crystals are formed which consist of 
a definite compound of chlorine and water containing 35-5 parts of the 
former to 90 of the latter. 

Chlorine has a specific gravity of 2-47, 100 cubic inches weighing 76-6 
grains. Exposed to a pressure of about four atmospheres, it condenses to 
a yellow limpid liquid. 

This substance has but little attraction for oxygen, its chemical energies 
being principally exerted towards hydrogen and the metals. When a lighted 
taper is plunged into the gas, it continues to burn with a dull red light, and 
emits a large quantity of smoke, the hydrogen of the wax being alone con- 
sumed, and the carbon separated. If a piece of paper be wetted with oil 
of turpentine, and thrust into a bottle filled with chlorine, the chemical 
action of the latter upon the hydrogen is so violent as to cause inflammation, 
accompanied by a copious deposit of soot. Although chlorine can, by indi- 
rect means, be made to combine with carbon, yet this never occurs under 
the circumstances described. 

Phosphorus takes fire spontaneously in chlorine ; it burns with a pale and 
feebly luminous flame. Several of the metals, as copper-leaf, powdered 
antimony, and arsenic, undei'go combustion in the same manner. A mixture 
of equal measures chlorine and hydrogen explodes with violence on the pas- 
sage of an electric spark, or on the application of a lighted taper, hydro- 
chloric acid gas being formed. Such a mixture may be retained in the dark 
for any length of time without change ; exposed to diffuse daylight, the two 
gases slowly unite, while the direct rays of the sun induce instantaneous 
explosion. 

The most characteristic property of chlorine is its bleaching power ; the 
most stable oi'ganic colouring principles are instantly decomposed and de- 
stroyed by this remarkable agent: indigo, for example, which resists the ac- 
tion of strong oil of vitriol, is converted by chlorine into a brownish sub- 
stance, to which the blue colour cannot be restored. The presence of water 
is essential to these changes, for the gas in a state of perfect dryness is in 
capable even of affecting litmus. 



CHLORINE. 141 

Chlorine is largely used in the arts for bleaching linen and cotton goods, 
rags for the manufacture of paper, &c. For these purposes, it is sometimes 
employed in the state of gas, sometimes in that of solution in water, but 
more frequently in combination with lime, forming the substance called 
bleaching-powder. When required in large quantities, it is often made by 
pouring slightly diluted oil of vitriol upon a mixture of common salt and 
oxide of manganese contained in a large leaden vessel. The decomposition 
which ensues may be thus represented : — 

Chloride of S Chlorine Chlorine. 

sodium ) Sodium _____________^ 

Sulphuric acid ^I^^rrs s— Sulphate of soda. 

Binoxideof f g^de of 

manganese | manganese 

Sulphuric acid — ^^ — — S Sulphate of man- 

f ganese 

Chlorine is one of the best and most potent substances that can be used 
for the purpose of disinfection, but its employment requires care. Bleach- 
ing-powder mixed with water, and exposed to the air in shallow vessels, be- 
comes slowly decomposed by the carbonic acid of the atmosphere, and the 
chlorine evolved ; if a more rapid disengagement be wished, a little acid of 
any kind may be added. In the absence of bleaching-powder, either of the 
methods for the production of the gas described may be had recourse to, 
always taking care to avoid an excess. 

Chloride of Hydrogen ; Hydrochloric, Chlorhydric or Muriatic Acid. — This 
substance in a state of solution in water, has been long known. The gas is 
prepared with the utmost ease by heating in a flask, fitted with a cork and 
bent tube, a mixture of common salt and oil of vitriol, diluted with a small 
quantity of water ; it must be collected by displacement, or over mercury. 
It is a colourless gas, which fumes strongly in the air from condensing the 
atmospheric moisture ; it has an acid, suffocating odour, but is infinitely less 
offensive than chlorine. Exposed to a pressure of 40 atmospheres, it 
liquefies. 

Hydrochloric acid gas has a density 1-269. It is exceedingly soluble in 
water, that liquid taking up at the temperature of the air about 418 times 
its bulk. The gas and solution are powerfully acid. 

The action of oil of vitriol on common salt, or any analogous substance, is 
thus easily explained : — 



Chlorine - Hydrochloric acid. 

Sodium 




Chloride of sodium 

Water 

Sulphuric acid ~ ~~ ^^^- ^ Sulphate of soda 

The composition of this substance may be determined by synthesis : when 
a measure of chlorine and a measure of hydrogen are fired by the electric 
spark, two measures of hydrochloric acid gas result, the combination being 
unattended by change of volume. By weight it contains 35-5 parts chlorine 
and 1 part hydrogen. 

Solution of hydrochloric acid, the liquid acid of commerce, is a very im- 
portant preparation, and of extensive use in chemical pursuits ; it is best 
prepared by the following arrangement : 

A large glass flask, containing a quantity of common salt, is fitted with a 



142 



CHLORINE. 



cork and bent tube, in the manner represented in fig. 106 ; the latter passes 
through and below a second short tube into a wide-necked bottle, containing 



Fig. 106 




a little water, into which the open tube dips. A bent tube is adapted to an- 
other hole in the cork of the wash-bottle, so as to convey the purified gas 
into a quantity of distilled water, by which it is instantly absorbed. The 
joints are made air-tight by melting over the coi-ks a little yellow wax. 

Oil of vitriol, about equal in weight to the salt, is then slowly introduced 
by the funnel ; the disengaged gas is at first wholly absorbed by the water 
in the wash-bottle, but when this becomes saturated, it passes into the 
second vessel and there dissolves. When all the acid has been added, heat 
may be applied to the flask by a charcoal chauffer, until its contents appear 
nearly dry, and the evolution of gas almost ceases, when the process may 
be stopped. As much heat is given out during the condensation of the gas, 
it is necessary to surround the condensing-vessel with cold water. 

The simple wash-bottle figured in the drawing will be found an exceed- 
ingly useful contrivance in a great number of chemical operations. It serves 
in the present, and in many similar cases, to retain any liquid or solid matter 
mechanically carried over with the gas, and it may be always employed when 
gas of any kind is to be passed through an alkaline or other solution. The 
open tube dipping into the liquid prevents the possibility of absorption, by 
which a partial vacuum would be occasioned, and the liquid of the second 
vessel lost by bein<L, driven into the first. 

The arrangement by which the acid is introduced, also deserves a moment's 
notice. The tube is bent twice upon itself, and a bulb blown in one portion. 
(Fig. 107.) Liquid poured into the funnel rises upon the opposite side of 



CnLORINE. 1-13 

the first bend until it reaches the second ; it then flows over and runs into 
the flask. Any quantity can then be got into the latter without the 
introduction of air, and -without the escape of gas from the inte,- Fig- 107. 
rior. The funnel acts also as a kind of safety-valve, and in both 
directions ; for if by any chance the delivery-tube should be stopped 
and the issue of gas prevented, its increased elastic force soon drives 
the little column of liquid out of the tube, the gas escapes, and the 
vessel is saved. On the other hand, any absorption within is quickly 
compensated by the entrance of air through the liquid in the bulb. 
The plan employed on the great scale by the manufacturer is the 
same in principle as that described ; he merely substitutes a large 
iron cylinder for the flask, and vessels of stone-ware for those of 
glass. 

Pure solution of hydrochloric acid is transparent and colourless ; 
when strong, it fumes in the air by disengaging a little gas. It 
leaves no residue on evaporation, and gives no precipitate or milki- 
ness with solution of chloride of barium. When saturated with the 
gas, it has a specific gravity of 1*21, and contains about 42 per cent, 
of real acid. 'T>he commercial acid has usually a yellow colour, and 
is very impure^ containing salts, sulphuric acid, chloride of iron, and 
organic matter^ It may be rendered sufficiently good for most pur- 
poses by diluting it to the density of 1-1, which happens when the strong 
acid is niixM w?fh its own bulk or rather less of water, and then distilling it 
in a retort furnished with a Liebig's condenser. 

A mixture of nitric and hydrochloric acids has long been known under the 
name of aqua rfjjea,#bm its property of dissolving gold. When these two 
substances are headed together, they both undergo decomposition, hyponitric 
acid and chlorine being evolved. This at least appears to be the final result 
of the action ; at a certain stage, however, two peculiar substances, con- 
sisting of nitrogen, oxygen, and chlorine, (chlorohyponitric acid 1 and chlo- 
ronitrous acu3^f\appear to be formed. It is chiefly the chlorine which 
attacks the nietahjL 

The presence oF hydrochloric acid, or any other soluble chloride, is easily 
detected by s^utron of nitrate of silver. A white curdy precipitate is pro- 
duced, insoluble in nitric acid, freely soluble in ammonia, and subject to 
blacken by exposure to light. 

Compounds of Chlorine and Oxygen. 
Although these bodies never combine directly, they may be made to unite 
by circuitous means in five different proportions, as below : — 

Composition by weight. 

Chlorine. Oxygen. 

Hypochlorous acid 35-5 8 

Chlorous acid 35-5 24 

Hypochloric acid.... 35-5 32 

Chloric acid 35-5 40 

Perchloric acid 3 35-5 56 

Hypochlorous and chloric acids are generated by the action of chlorine on 
certain metallic oxides ; the former in the cold, the latter at a high tenipe • 

1 NOa CI* a XO2CI. 

* Hypochlorous acid CIO 

Chlorous acid C103 

Hypochloric acid CIO4 

Chloric acid CIO5 

Perchloric acid C107 




144 CHLORINE. 

rature. Chlorous, hypocliloric, and perchloric acids result from the decom- 
position of chloric acids. 

Hypochlorous Acid. — This is "best prepared by the action of chlorine gas 
upon red oxide of mercury. It is a pale yellow gaseous body, containing, 
in every two measures, two measures of chlorine and one of oxygen. It is 
very freely soluble in water, and explodes, although with no great violence, 
by slight elevation of temperature. The odour of this gas is peculiar, and 
but remotely resembles that of chlorine. It bleaches powerfully, and acts 
upon certain of the metals in a manner which is determined by their re- 
spective attractions for oxygen and chlorine. It forms with the alkalis a 
series of bleaching salts. 

The preparations called chloride of, or chlorinated lime and soda, contain 
hj'pochlorous acid. A description of these will be found under the head of 
Salts of Lime. 

The reaction by which hypochlorous acid is produced may thus be illus- 
trated : — 

Chlorine — r== ^ Hypochlorous acid. 

Oxide of f Mercury 
ry \ Oxi 



mercury 

Chlorine ' ^~^-~ -Chloride of mercury. 

The chloride of mercury, however, does not remain as such ; it combines 
with another portion of the oxide, when the latter is in excess, forming a 
peculiar brown compound, an oxychloride of mercury. 1 

Chlorous Acid. — This substance is prepared by heating in a flask filled to 
the neck, a mixture of 4 parts of chlorate of potassa and 3 parts of arsenious 
acid with 12 parts of nitric acid previously diluted by 4 parts of water. 
During the operation, which must be performed in a water-bath, a greenish 
yellow gas is evolved, which is sparingly soluble in water, and cannot be 
condensed by exposure to a freezing mixture. It slowly combines with 
bases, producing a class of salts called chlorites. The process which gives 
rise to chlorous acid is rather complicated. The arsenious acid deprives the 
nitric acid of part of its oxygen, reducing it into nitrous acid, which is 
oxidized again at the expense of the chloric acid. This, by the loss of two- 
fifths of its oxygen, becomes chlorous acid. 

Hypochloric Acid; Peroxide of Chlorine. — Chlorate of potassa is made into 
a paste with concentrated sulphuric acid, and cooled ; this is introduced into 
a small glass retort, and very cautiously heated by warm water ; a deep 
yellow gas is evolved, which is the body in question; it can be collected only 
V>y displacement, since mercury decomposes, and water absorbs the gas. 

Hypochloric acid has a powerful odour, quite different from that of the 
preceding compounds, and of chlorine itself. It is exceedingly explosive, 
being resolved with violence *into its elements by a temperature short of the 
boiling point of water. Its preparation is, therefore, always attended by 
danger, and should be performed only on a small scale. It is composed 
Dy measure of one volume of chlorine and two volumes of oxygen, con- 

1 A very commodious method of preparing hypochlorous acid has lately heen described by 
M. Pelouze. Red oxide of mercury, prepared by precipitation and dried by exposure to a 
etrong heat, is introduced into a glass tube, kept cool, and well washed, and dry chlorine gas is 
elowly passed over it. Chloride of mercury and hypochlorous acid are formed; the latter is 
collected by displacement. "When the flask or bottle in which the gas is received is exposed 
to artificial cold by the aid of a mixture of ice and salt, the hypochlorous acid condenses to a 
deep red liquid, slowly soluble in water, and very subject to explosion. It is remarkable that 
the crystalline oxide of mercury prepared by calcining the nitrate, or by the direct oxidation 
of the metal, is scarcely acted upon by chlorine under the circumstances described, — Amx 
Chini. et Phys. 3d series, vii. 179. 



CHLORINE. 



145 



Me. 108. 



lensed into two volumes. 1 It may be liquefied by cold. The solution of the 
gas in water bleaches. Salts of this acid have not yet been obtained. 

The euchlorine of Davy, prepared by gently heating chlorate of potassa 
with dilute hydrochloric acid, is probably a mixture of chlorous acid and 
free chlorine. 

The production of chlorous acid from chlorate of potassa and sulphuric 
acid, depends upon the spontaneous splitting of the chloric acid into chlorous 
acid and perchloric acid, which latter remains in union with the potassa. 3 

When a mixture of chlorate of potassa and sugar is touched with a drop 
of oil of vitriol, it is instantly set on fire ; the hypochloric acid disengaged 
being decomposed by the combustible substance with 
such violence as to cause inflammation. If crystals 
of chlorate of potassa be thrown into a glass of water, 
a few small fragments of phosphorus added, and 
then oil of vitriol poured down a narrow funnel 
reaching to the bottom of the glass, the phosphorus 
will burn beneath the surface of the water by the as- 
sistance of the oxygen of the hypochloric acid disen- 
gaged. Fig. 108. The liquid at the same time 
becomes yellow, and acquires the odour of that gas. 

Chloric Acid. — This is the most important com- 
pound of the series. When chlorine is passed to 
saturation into a moderately strong hot solution of 
caustic potassa, or the carbonate of that base, and 
the liquid concentrated by evaporation, it furnishes, 
on cooling, flat tubular crystals of a colourless salt, 
consisting of potassa combined with chloric acid. 
The mother-liquor contains chloride of potassium. In this reaction a part 
of the potassa is decomposed ; its oxygen combines with one portion of 
chlorine to form chloric acid, while the potassium is taken up by a second 
portion of the same substance. 3 

From chlorate of potassa, chloric acid may be obtained by boiling the 
salt with a solution of hydrofluosilicic acid, which forms an almost insoluble 
salt with potassa, decanting the clear liquid, and digesting it with a little 
silica, which removes the excess of the hydrofluosilicic acid. Filtration 
through paper must be avoided. 

By cautious evaporation, the acid may be so far concentrated as to assume 
a syrupy consistence ; it is then very easily decomposed. It sometimes sets 
fire to paper, or other dry organic matter, in consequence of the facility with 
which it is deoxidized by combustible bodies. 

The chlorates are easily recognized ; they give no precipitate when in 
solution with nitrate of baryta or silver; they evolve pure oxygen when 
heated, passing thereby into chlorides ; and they afford, when treated with 
sulphuric acid, the characteristic explosive yellosv gas already described. 
The dilute solution of the acid has no bleaching power. 

Perchloric Acid. — Prof. Penny has shown that when powdered chlorate of 
potassa is thrown by small portions into hot nitric acid, a change of the 




1 In equivalents, as already stated, CIO4. 

C 2 eq. chlorine 
3 3 equiv. chloric acid< 8 cq. oxygen 

(_ 7 eq. oxygen - 
1 eq. chlorine ■ 

'« -* ■**■*» f is 5332- 



2 eq. hyrochloric acid. 



T 5 eq. potassium 

sa -< 



eq. potassa -{ 5 eq. oxygen 
(^ 1 eq. potassa 



= — 1 eq. perchloric acid. 
^ 5 eq. chloride potassium. 



1 eq. chlorate pctassa. 



MG IODINE. 

same description as that which happens when sulphuric acid is used takes 
place, but with this important difference, that the chlorine and oxygen, 
instead of being evolved in a dangerous state of combination, are emitted in 
a state of mixture. The result of the reaction is a mixture of nitrate of 
potassa and perchlorate of potassa, which may be readily separated by their 
difference of solubility. 

By treating the potassa salt in the manner directed for chloric acid, the 
free acid may be obtained tolerably pure. It may be concentrated by evapo- 
ration, and even distilled without change. The solution fumes slightly in 
the air, and has a specific gravity of 1-65. It is very greedy of moisture, 
and has no bleaching properties. The pei'chlorates much resemble the chlo- 
rates ; they give off oxygen when heated to redness. The acid is the most 
stable of the compounds of chlorine and oxygen. 

IODINE. 

This remarkable substance was first noticed in 1812 by M. Courtois of 
Paris. Minute traces are found in combination with sodium or potassium 
in sea-water, and occasionally a much larger proportion in that of certain 
mineral spi'ings. It seems to be in some way beneficial to many marine 
plants, as these latter have the power of abstracting it from the surrounding 
water, and accumulating it in their tissues. It is from this source that all 
the iodine of commerce is derived. It has lately been found in minute 
quantity in some aluminous slates of Sweden, and in several varieties of 
coal and turf. 

Kelp, or the half-vitrified ashes of sea-weeds, prepared by the inhabitants 
of the Western Islands and the northern shores of Scotland and Ireland, is 
treated with water, and the solution filtered. The liquid is then concentrated 
by evaporation until it is reduced to a very small volume, the chloride of 
sodium, carbonate of soda, chloride of potassium, and other salts, being 
removed as they successively crystallize. The dark brown mother-liquor 
left contains very nearly the whole of the iodine ; this is mixed with sul- 
plnvric acid and binoxide of manganese, and gently heated in a leaden retort, 
when the iodine distils over and condenses in the receiver. The theory of 
the operation is exactly analogous to that of the preparation of chlorine ; 
it requires in practice, however, careful management, otherwise the impuri- 
ties present in the solution interfere with the general result. 

The manganese is not really essential ; iodide of potassium or sodium, 
heated with an excess of sulphuric acid, evolves iodine. This effect is due 
to a secondary action between the hydriodic acid first produced, and the 
excess of the sulphuric acid, in which both suffer decomposition, yielding 
iodine, water, and sulphurous acid. 

Iodine crystallizes in plates or scales of a bluish-black colour and imper- 
fect metallic lustre, resembling that of plumbago ; the crystals ai*e sometimes 
?ery large and brilliant. Its density is 4-948. At 225° (107°-2C) it fuses, 
and at 317° (175°C) boils, the vapour having an exceedingly beautiful violet 
colour. 1 It is slowly volatile, however, at common temperatures, and exhales 
an odour much resembling that of chlorine. The density of the vapour is 
8-71G. Iodine requires for solution about 7000 parts of water, which never- 
theless acquires a brown colour ; in alcohol it is much more freely soluble. 
Solutions of hydriodic acid and the iodides of the alkaline metals also dis- 
solve a large quantity ; these solutions are not decomposed by water, which 
is the case with the alcoholic tincture. 

This substance stains the skin, but not permanently; it has a very ener- 
getic action upon the animal system, and is much used in medicine. 

1 Whence the name, luc,',g, violet-coloured. 



IODINE 



147 



Tig. 109. 



One of the most characteristic properties of iodine is the production of a 
splendid blue colour by contact with the organic principle starch. The iodine 
for this purpose must be free or uncombined. It is easy, however, to make the 
test available for the purpose of recognizing the presence of the element in 
question when a soluble iodide is suspected ; 
it is only necessary to add a very small quan- 
tity of chlorine-water, when the iodine, being 
displaced from combination, becomes capable 
of acting upon the starch. 

Hydriodic Acid. — The simplest process for 
preparing hydriodic acid gas is to introduce 
into a glass tube (fig. 109), sealed at one 
extremity, a little iodine, then a small quan- 
tity of roughly-powderefd glass moistened 
with water, upon this a few little fragments 
of phosphorus, and lastly more glass ; this 
order of iodine, glass, phosphorus, glass, is 
repeated until the tube is half or two-thirds 
filled. A cork and narrow bent tube are 
then fitted, and gentle heat applied. The 
gas is received over mercury. The experi- 
ment depends upon the formation of an 
iodide of phosphorus, and its subsequent 
decomposition by water, hydrated phospho- 
rous acid and iodide of hydrogen being produced. The glass merely serves 
to moderate the violence of the action of the iodine upon the phosphorus. 

Hydriodic acid gas greatty resembles the corresponding chlorine compound ; 
it is colourless, and highly acid ; it fumes in the air, and is very soluble in 
water. Its density is about 4-4. By weight it is composed of 127 parts iodine 
and 1 part hydrogen ; and by measure, of equal volumes of iodine-vapour 
and hydrogen united without condensation. 

Solution of hydriodic acid may be prepared by a process much less trou- 
blesome than the above. Iodine in fine powder is suspended in water, and 
a stream of washed sulphuretted hydrogen passed through the mixture ; 
sulphur is deposited, and the iodine converted into hydriodic acid. When 
the liquid has become colourless, it is heated to expel the excess of sulphu- 
retted hydrogen, and filtered. This solution cannot long be kept, especially 
if it be strong ; the oxygen of the air gradually decomposes the hydriodic 
acid, and iodine is set free, which, dissolving in the remainder, communicates 
to it a brown colour. 




Compounds of Iodine and Oxygen. 
The most important of these are the iodic and periodic acids. 



Composition by weight. 



Iodine. 

Iodic acid 127 

Periodic acid 1 127 



Oxygen. 

... 40 
.. 56 



Iodic Acid may be prepared by the direct oxidation of iodine by nitric acm 
of specific gravity 1-5 ; 5 parts of dry iodine with 200 parts of nitric acid 
are kept at a boiling temperature for several hours, or until the iodine has 
disappeared. The solution is then cautiously distilled to dryness, and the 
residue dissolved in water and made to crystallize. 



I0 5 , and 107. 



148 BROMINE. 

Iodic acid is a very soluble substance; it crystallizes in colourless, six- 
sided tables, which contain water. It is decomposed by heat, and its solution 
readily deoxidized by sulphurous acid. The iodates much resemble the 
chlorates ; that of potassa is decomposed by heat into iodide of potassium 
and oxygen gas. 

Periodic Acid. — When solution of iodate of soda is mixed with caustic 
soda, and a current of chlorine transmitted through the liquid, two salts are 
formed, namely, chloride of sodium and a combination of periodate of soda 
with hydrate of soda, which is sparingly soluble. This is separated, con- 
certed into a silver-salt, and dissolved in nitric acid ; the solution yields on 
evaporation crystals of yellow periodate of silver ; from which the acid may 
be separated by the action of water, which resolves the ■ salt into free acid 
and insoluble basic periodate. 

The acid itself may be obtained in crystals. It is permanent in the air, 
and capable of being resolved into iodine and oxygen by a high temperature, 

BROMINE. 

Bromine * dates back to 1826 only, having been discovered by M. Balard of 
Montpelier. It is found in sea- water, and is a frequent constituent of saline 
springs, chiefly as bromide of magnesium ; — a celebrated spring of the kind 
exists near Kreuznach in Prussia. Bromine may be obtained pure by the 
following process, which depends upon the fact, that ether agitated with 
an aqueous solution of bromine, removes the greater part of that substance. 

The mother-liquor, from which the less soluble salts have separated by 
crystallization, is exposed to a stream of chlorine, and then shaken up with 
a quantity of ether; the chlorine decomposes the bromide of magnesium, 
and the ether dissolves the bromine thus set free. On standing, the ethereal 
solution, having a fine red colour, separates, and may be removed by a funnel 
or pipette. Caustic potassa is then added in excess, and heat applied ; 
bromide of potassium and bromate of potassa are formed. The solution is 
evaporated to dryness, and the saline matter, after ignition to redness to 
decompose the bromate of potassa, heated in a small retort with binoxide 
of manganese and sulphuric acid diluted with a little water, the neck of the 
retort being plunged into cold water. The bromine volatilizes in the form 
of a deep red vapour, which condenses into drops beneath the liquid. 

Bromine is at common temperatures a red thin liquid of an exceedingly 
intense colour, and very volatile; it freezes at about 19° ( — 7°-2C), and 
boils at 145°-4 (63°C). The density of the liquid is 2-976, and that of the 
vapour 5-39. The odour of bromine is very suffocating and offensive, much 
resembling that of iodine, but more disagreeable. It is slightly soluble in 
water, more freely in alcohol, and most abundantly in ether. The aqueous 
solution bleaches. 

Hydrobromic Acid. — This substance bears the closest resemblance in every 
particular to hydriodic acid ; it has the same constitution by volume, very 
nearly the same properties, and may be prepared by means exactly similar, 
substituting the one body for the other. The solution of hydrobromic acid 
has also the power of dissolving a large quantity of bromine, thereby acquir- 
ing a red tint. Hydrobromic acid contains by weight 80 parts bromine, 
and 1 part hydrogen. 

Bromic Acid. — Caustic alkalis in presence of bromine undergo the same 
change as with chlorine, bromide of the metal and bromate of the oxide 
being produced; these may often be separated by the inferior solubility of 

1 From SpGJuog, a noisome smell : a very appropriate term. 



FLUORINE — SILICIUM. 149 

the latter. Bromic acid, obtained from bromate of baryta, closely resembles 
chloric acid ; it is easily decomposed. The bromates -when heated lose 
oxygen and become bromides. 
No other compound of bromine and oxygen has yet been described. 

FLFORIXE 

This element has never been isolated, at least in a state fit for examination ; 
its properties are consequently in great measure unknown ; from the obser- 
vations made, it is presumed to be gaseous, and to possess colour, like 
chlorine. The compounds containing fluorine can be easily decomposed, and 
the element transferred from one body to another; but its extraordinary 
chemical energies towards the metals and towards silicium, a component of 
glass, have hitherto baffled all attempts to obtain it pure in a separate state. 
As fluoride of calcium it exists in small quantities in many animal substances : 
such as bones. Several chemists have endeavoured to obtain it by decom- 
posing fluoride of silver by means of chlorine in vessels of fluor-spar, but 
even these experiments have not led to a decisive result. 

Hydrofluoric Acid. — When powdered fluoride of calcium (fluor-spar) is 
heated with concentrated sulphuric acid in a retort of platinum or lead con- 
nected with a carefully cooled receiver of the same metal, a very volatile 
colourless liquid is obtained, which emits copious white and highly suffoca- 
ting fumes in the air. This was formerly believed to be the acid in an 
anhydrous state. M. Louyet, however, states that it still contains water, 
and that hydrofluoric acid, like hydrochloric acid, when anhydrous, is a gas. 

When hydrofluoric acid is put into water, it unites with the latter with 
great violence ; the dilute solution attacks glass with great facility. The 
concentrated acid dropped upon the skin occasions deep and malignant ulcers, 
so that great care is requisite in its management. Hydrofluoric acid contains 
19 parts fluorine and 1 part hydrogen. 

In a diluted state, this acid is occasionally used in the analysis of siliceous 
minerals, when alkali is to be estimated ; it is employed also for etching on 
glass, for which purpose the acid may be prepared in vessels of lead, that 
metal being but slowly attacked under these circumstances. The vapour of 
the acid is also very advantageously applied to the same object in the fol- 
lowing manner : the glass to be engraved is coated with etching-ground or 
wax, and the design traced in the usual way with a pointed instrument. A 
shallow basin made by beating up a piece of sheet lead is then prepared, a 
little powdered fluor-spar placed in it, and enough sulphuric acid added to 
form with the latter a thin paste. The glass is placed upon the basin, with 
the waxed side downwards, and gentle heat applied beneath, which speedily 
disengages the vapour of hydrofluoric acid. In a very few minutes the ope- 
ration is complete ; the glass is then removed and cleaned by a little warm 
oil of turpentine. When the experiment is successful, the lines are very 
clear and smooth. 

No combination of fluorine and oxygen has yet been discovered. 

SILICIUM. 

Silicium, sometimes called silicon, in union with oxygen constituting silica, 
or the earth of flints, is a very abundant substance, and one of great im- 
portance. It enters largely into the composition of many of the rocks and 
mineral masses of which the surface of the earth is composed. The following 
process yields silicium most readily. The double fluoride of silicium and 
potassium is heated in a glass tube with nearly its own weight of metallic 
potassium ; violent reaction ensues, and silicium is set free. When cold, 
ths contents of the tube are put into cold water, which removes the saline 
13* 



150 



SILICIUM. 



Fig. 110 



matter and any residual potassium, and leaves untouched the silicium. So 
prepared, silicium is a dark brown powder, destitute of lustre. Heated in 
the air, it burns, and becomes superficially converted into silica. It is also 
acted upon by sulphur and by chlorine. When silicium is strongly heated in 
a covered crucible, its properties are greatly changed ; it becomes darker in 
colour, denser, and incombustible, refusing to burn even when heated by the 
flame of the oxy-hydrogen blowpipe. 

Silica. — This is the only known oxide; it contains 21-3 parts silicium, and 
24 parts oxygen. 1 Colourless transparent rock-crystal consists of silica very 
nearly in a state of purity ; common quartz, agate, cfalcedony, flint, and 
several other minerals, are also chiefly composed of this substance. 

The experiment about to be described, furnishes silica in a state of com- 
plete purity, and at the same time ex- 
hibits one of the most remarkable pro- 
perties of silicium, namely, its attraction 
for fluorine. A mixture is made of equal 
parts fluor-spar and glass, both finely 
powdered, and introduced into a glass 
flask, with a quantity of oil of vitriol. A 
tolerably wide bent tube, fitted to the 
flask by a cork, passes to the bottom of a 
glass jar, into which enough mercury is 
poured to cover the extremity of the 
tube. The jar is then half filled with 
water, and heat is applied to the flask. 
(Fig. 110.) 

The first effect is the disengagement 
of hydrofluoric acid ; this substance, how- 
ever, finding itself in contact with the 
silica of the powdered glass, undergoes 
decomposition, water and flouride of silicium being produced. The latter is 
a permanent gas, which escapes from the flask by the bent tube. By con- 
tact with a large quantity of water, it is in turn decomposed, yielding silica, 
which separates in a beautiful gelatinous condition, and an acid liquid which 
is a double fluoride of silicium and hydrogen, commonly called hydrofluo- 
silicic acid. 2 The silica may be collected on a cloth filter, well washed, dried, 
and heated to redness to expel water. 

The acid liquid is kept as a test for baryta and potassa, with which it 
forms nearly insoluble* precipitates, the double fluoride of silicium and potas- 
sium being used, as was stated, in the preparation of silicium. The fluoride 
of silicium, instead of being conducted into water, may be collected over 
mercury ; it is a permanent gas, destitute of colour, and very heavy. Ad- 
mitted into the air, it condenses the moisture of the latter, giving rise to a 




1 Or, Si0 3 . 

a (1) Reaction of hydrofluoric acid upon silica :- 

<™» {335? 



Gaseous fluoride of silicium. 



.Water. 



2) Decomposition of fluoride of silicium by water: — 
Fluoride of silicium j |S™ 

f Oxygen 
[ Hydrogen 

Fluorido of silicium , . ^ HydrofluosUicic acid. 



Water 




BORON. 151 

thick "white cloud. It is important in the expei-iment above described to 
keep the end of the delivery-tube from touching the water of the jar, other- 
wise it almost instantly becomes stopped ; the mercury effects this object. 

There is another method by which pure silica can be prepared, and which 
is also very instructive, inasmuch as it is the basis of the proceeding adopted 
in the analysis of all siliceous minerals. Powdered rock-crystal or fine sand 
is mixed with about three times its weight of dry carbonate of soda, and the 
mixture fused in a platinum crucible. When cold, the glassy mass is boiled 
with water, by which it is softened, and almost entirely dissolved. An excess 
of hydrochloric acid is then added to the filtered liquid, and the whole eva- 
porated to complete dryness. By this treatment the gelatinous silica thrown 
down by the acid becomes completely insoluble, and remains behind when 
the dry saline mass is treated with acidulated water, by which the alkaline 
salts, alumina, sesquioxide of iron, lime, and many other bodies which may 
happen to be present, are removed. The silica is washed,, dried, and heated 
red-hot. 

The most prominent characters of silica are the following : it is a very 
fine, white, tasteless powder, not sensibly soluble in water or dilute acids 
(with the exception of hydrofluoric) unless recently precipitated. It dis- 
solves, on the contraiy, freely in strong alkaline solutions. Its density is 
about 2-66, and it is only to be fused by the oxy-hydrogen blowpipe. 

Silica is in reality an acid, and a very powerful one ; insolubility in water 
prevents the manifestation of acid properties under ordinary circumstances. 
When heated with bases, especially those which are capable of undergoing 
fusion, it unites with them and forms true salts, which are sometimes solu- 
ble in water, as in the case of the silicates of potassa and soda when the 
proportion of base is considerable. Common glass is a mixture of several 
silicates in which the reverse of this happens, the silica, or as it is more cor- 
rectly called, silicic acid, being in excess. Even glass, however, is slowly 
acted upon by water. 

Finely-divided silica is highly useful in the manufacture of porcelain. 

BOEON. 

This substance is closely related to silicium ; it is the basis of boracic 
acid. 

Boron is prepared by a process very similar to that described in the case 
of silicium, the double fluoride of boron and potassium being substituted for 
the other salt, and the operation conducted in a small iron vessel instead of 
a glass tube. It is a dull greenish-brown powder, which burns in the air 
when heated, producing boracic acid. Nitric acid, alkalis in a fused condi- 
tion, chlorine, and other agents, attack it readily. 

There is but one oxide of boron, namely, boracic acid, containing 109 parts 
boron and 24 parts oxygen. 1 

Boracic acid is found in solution in the water of the hot volcanic lagoons 
of Tuscany, whence a large supply is at present derived. It is also easily 
made by decomposing with sulphuric acid a hot solution of borax, a salt 
brought from the East Indies, consisting of boracic acid combined with soda. 

Boracic acid crystallizes in transparent colourless plates, soluble in- about 
25 parts of cold water, and in a much smaller quantity at a boiling heat ; 
the acid has but little taste, and feebly affects vegetable colours. W T hen 
heated, it loses water, and melts to a glassy transparent mass, which dis- 
solves many metallic oxides with great ease. The crystals contain 34-9 
parts real acid, and 27 parts water. They dissolve in alcohol, and the solu- 
tion burns with a green flame. 

»B0 3 . 



152 BORON. 

Glassy boracic acid in a state of fusion requires for its dissipation in 
vapour a very intense and long-continued heat; the solution in water cannot, 
however, be evaporated without very appreciable loss by volatilization ; 
hence it is probable that the hydrate is far more volatile than the acid itself. 

By heating in a glass flask or retort one part of the vitrified boracic acid, 
2 of fluor-spar, and 12 of oil of vitriol, a gaseous fluoride of boron may be 
obtained, and received in glass jars standing over mercury. It is a trans- 
parent gas, very soluble in water, and very heavy ; it forms a dense fume in 
the air like the fluoride of silicium. 1 



1 These two bodies are thus constituted : — SiFs, and BFg. 



COMPOUNDS OF CARBON AND HYDROGEN. IfH 



ON CERTAIN IMPORTANT COMPOUNDS FORMED BY THE UNION OF 
THE PRECEDING ELEMENTS AMONG THEMSELVES. 

1 

COMPOUNDS OF CARBON AND HYDROGEN. 

The compounds of carbon and hydrogen already known are exceedingly 
numerous ; perhaps all, in strictness, belong to the domain of organic che- 
mistry, as they cannot be formed by the direct union of their elements, but 
always arise from the decomposition of a complex body of organic origin. 
It will be found convenient, notwithstanding, to describe two of them in this 
part of the volume, as they very well illustrate the important subjects of 
combustion, and the nature of flame. 

Light Carbonetled or Carburetted Hydrogen ; dfarsh-gas ; Fire-damp ; Gas of 
the Acetates. — This gas is but too often found to be abundantly disengaged in 
coal-mines from the fresh-cut surface of the coal, and from remarkable aper- 
tures or "blowers," which emit for a great length of time a copious stream 
or jet of gas, which probably existed in a state of compression, pent up in 
the coal. 

The mud at the bottom of pools in which water-plants grow, on being 
stirred, suffers bubbles of gas to escape, which may be easily collected. 
This, on examination, is found to be chiefly a mixture of light carbonetted 
hydrogen and carbonic acid ; the latter is easily absorbed by lime-water or 
caustic potassa. 

Until recently, no method was known by which the gas in question could 
be produced in a state approaching to purity by artificial means ; the various 
illuminating gases from pit-coal and oil, and that obtained by passing the 
vapour of alcohol through a red-hot tube, contain large quantities of light 
carbonetted hydrogen, associated, however, with other substances whicli 
hardly admit of separation. M. Dumas was so fortunate as to discover a 
method by which that gas can be produced at will, perfectly pure, and in 
any quantity. 

A mixture is made of 40 parts crystallized acetate of soda, 40 parts solid 
hydrate of potassa, and 60 parts quicklime in powder. This mixture is 
transferred to a flask or retort, and strongly heated ; the gas is disengaged 
in great abundance, and may be received over water. 1 

Light carbonetted hydrogen is a colourless and nearly inodorous gas, which 
does not affect vegetable colours. It burns with a yellow flame, generating 

1 Ann. Cbim. et Phys. Ixxiii. 93. The reaction consists in the conversion of the acetic acid, 
by the aid of the elements of water, into carbonic acid and light carbonetted hydrogen; the 
instability of the organic acid at a high temperature, and the attraction of the potassa for 
carbonic acid, being the determining causes. The lime prevents the hydrate of potassa from 
fusing and attacking the glass vessels. This decomposition is best understood by putting it 
in the shape of an equation. 

Acetic acid C4H3O3 \_( Carbonic acid. 2 eq. C 2 O4. 
Water H j \ Marsh-gas, 2 eq. C2H4 

C4H4O4. C1II4O4. 



154 COMPOUNDS OF 

carbonic acid and water. It is not poisonous, and may be respired to a great 
extent without apparent injury. The density of this compound is about 
0-559, 100 cubic inches weighing 17-41 grains; and it contains carbon and 
hydrogen associated in the proportion of 6 parts by weight of the former to 
2 of the latter. 1 

"When 100 measures of this gas are mixed with 200 of pure oxygen in the 
eudiometer, and the mixture exploded by the electric spai'k, 100 measures 
of a gas remain which is entirely absorbable by a little solution of caustic 
potassa. Now carbonic acid contains its own volume of ox} r gen ; hence one- 
half of the oxygen added, that is, 100 measures, must have been consumed 
in uniting with the hydrogen. Consequently, the gas must contain twice its 
own measure of hydrogen, and enough carbon to produce, when completely 
burned, an equal quantity of carbonic acid. 

When chlorine is mixed with light carbonetted hydrogen over water, no 
change follows, provided light be excluded. The presence of light, however, 
brings about decomposition, hydrochloric acid, carbonic acid, and sometimes 
other products being produced. It is important to remember that the gas 
is not acted upon by chlorine in the dark. 

Olefiant Gas. — Strong spirit of wine is mixed with five or six times its 
weight of oil of vitriol in a glass-flask, the tube of which passes into a wash- 
bottle containing caustic potassa. A second wash-bottle, partly filled with 
oil of vitriol, is connected to the first, and furnished with a tube dipping into 
the water of the pneumatic trough. On the first application of heat to the 
contents of the flask, alcohol, and afterwards ether, make their appearance ; 
but, as the temperature rises, and the mixture blackens, the ether-vapour 
diminishes in quantity, and its place becomes in great part supplied by a 
permanent inflammable gas ; carbonic acid and sulphurous acid are also 
generated at the same time, besides traces of other products. The two last- 
mentioned gases are absorbed by the alkali in the first bottle, and the ether 
vapour by the acid in the second, so that the olefiant gas is delivered tole- 
rably pure. The reaction is too complex to be discussed at the present mo- 
ment ; it will be found fully described in another part of the volume. Ole- 
fiant gas thus produced is colourless, neutral, and but slightly soluble in 
water. Alcohol, ether, oil of turpentine, and even olive oil, as Mr. Faraday 
has observed, dissolve it to a considerable extent. 3 It has a faint odour of 
garlic. On the approach of a kindled taper it takes fire, and burns with a 
splendid white light, far surpassing in brilliancy that produced by light car- 
bonetted hydrogen. This gas, when mixed with oxygen and fired, explodes 
with extreme violence. Its density is 0-981 ; 100 cubic inches weigh 30-57 
grains. 

By the use of the eudiometer, as already described, it has been found that 
each measure of olefiant gas requires for complete combustion exactly three 
of oxygen, and produces under these circumstances two measures of car- 
bonic acid. Whence it is evident that it contains twice its own volume of 
hydrogen, combined with twice as much carbon as in marsh-gas. 

By weight, these proportions will be 12 parts carbon, and 2 parts 
hydrogen. 

Olefiant gas is decomposed by passing through a tube heated to bright 
redness ; a deposit of charcoal takes place, and the gas becomes converted 

1 The two carbides of hydrogen here described are thus represented in equivalents: — 
Light carbonetted hydrogen C II 2 

Olefiaut gas C2H2 

54 Olefiant gas, by pressure and intense cold, produced by the evaporation in a vacuum of 
solid carbonic acid and ether, is condensed into a colourless transparent liquid, but not frozen. 
(Laraday.)— R. B. 



CARBON AND HYDROGEN. 355 

into light carbonetted hydrogen, or even into free hydrogen, if the temper- 
ature be very high. This latter change is of course attended by increase of 
•volume. 

Chlorine acts upon defiant gas in a very remarkable manner. When the 
two bodies are mixed, even in the dark, they combine in equal measures, and 
give rise to a heavy oily liquid, of sweetish taste and ethereal odour, to 
which the name chloride of hydrocarbon, or Dutch liquid, is given. It is 
from this peculiarity that the term olefiant is derived. 

A pleasing and instructive experiment may also be made by mixing in a 
tall jar two measures of chlorine and one of olefiant gas, and then quickly 
applying a light to the mouth of the vessel. The chlorine and hydrogen 
unite with flame, which passes quickly down the jar, while the whole of the 
carbon is set free in the form of a thick black smoke. 

Coal and Oil Gases. — The manufacture of coal-gas is at the present mo- 
ment a branch of industry of great interest and importance in several 
points of view. The process is one of great simplicity of principle, but 
requires, in practice, some delicacy of management to yield a good result. 

When pit-coal is subjected to destructive distillation, a variety of products 
show themselves ; permanent gases, steam, and volatile oils, besides a not 
inconsiderable quantity of ammonia from the nitrogen always present in the 
coal. These substances vary very much in their proportions with the tem- 
perature at which the process is conducted, the permanent gases becoming- 
more abundant with increased heat, but at the same time losing much of 
their value for the purposes of illumination. 

The coal is distilled in cast-iron retorts, maintained at a bright red heat, 
and the volatilized products conducted into a long horizontal pipe of large 
dimensions, always half filled with liquid, into which dips the extremity of 
each separate tube ; this is called the hydraulic main. The gas and its ac- 
companying vapours are next made to traverse a refrigerator, usually a 
series of iron pipes, cooled on the outside by a stream of water ; here the 
condensation of the tar and ammoniacal liquid becomes complete, and the 
gas proceeds onwards to another part of the apparatus, in which it is to be 
deprived of the sulphuretted hydrogen and carbonic acid gases always present 
in the crude product. This is generally effected by hydrate of lime, which 
readily absorbs the compounds in question. The purifiers are large iron 
vessels, partly filled with a mixture of hydrate of lime and water, in which 
a churning machine or agitator is kept in constant motion to prevent the 
subsidence of the lime. The gas is admitted at the bottom of the vessel by 
a great number of minute apertures, and is thus made to present a large 
surface of contact to the purifying liquid. The last part of the operation, 
which indeed is often omitted, consists in passing the gas through dilute 
sulphuric acid, in order to remove ammonia. The quantity thus separated 
is very small, relatively to the bulk of the gas, but in an extensive work be- 
comes an object of importance. 

Coal-gas thus manufactured and purified is preserved for use in immense 
cylindrical receivers, close at the top, suspended in tanks of water by chains 
to which counterpoises are attached, so that the gas-holders rise and sink 
in the liquid as they become filled from the purifiers or emptied by the main.-;. 
These latter are made of large diameter, to diminish as much as possible the 
resistance experienced by the gas in passing through such a length of pipe. 
The joints of these mains are yet made in such an imperfect manner, that 
immense loss is experienced by leakage when the pressure upon the gas at 
the works exceeds that exerted by a column of water an inch in height. l 

*It may give some idea of the extent of this species of manufacture, to mention, that in- 
tfc? year 1838, for lighting London and the suburbs alone, there were eighteen public gas 
work?, aud £2,500,000 invested iu pipes and apparatus. The yearly revenue amounted to 



156 COMBUSTION, AND 

Coal-gas varies much in composition, judging from its variable density 
and illuminating power, and from the analyses which have been made. The 
difficulties of such investigations are very great, and unless particular pre- 
caution be taken, the results are merely approximative. The purified gas is 
believed to contain the following substances, of which the first is most abun- 
dant, and the second most valuable. 

Light carbonetted hydrogen. 

Olefiant gas. 

Hydrogen. 

Carbonic oxide. 

Nitrogen. 

Vapours of volatile liquid carbides of hydrogen. 1 

Vapour of bisulphide of carbon. 

Separated by Condensation and by the Purifiers. 

Tar and volatile oils. 

Sulphate of ammonia, chloride and sulphide of ammonium. 

Sulphuretted hydrogen. 

Carbonic acid. 

Hydrocyanic acid, or cyanide of ammonium. 

A very far better illuminating gas may be prepared from oil, by dropping 
it into a red-hot iron retort filled with coke ; the liquid is in great part de- 
composed and converted into permanent gas, which requires no purification, 
as it is quite free from the ammoniacal and sulphur compounds which vitiate 
the gas from coal. A few years ago this article was prepared in London ; it 
was compressed for the use of the consumer into strong iron vessels, to the 
extent of 30 atmospheres ; these were furnished with a screw-valve of pecu- 
liar construction, and exchanged for others when exhausted. The comparative 
high price of the material, and other circumstances, led to the abandonment 
of the undertaking. 

COMBUSTION, AND THE STRUCTURE OF FLAME. 

When any solid substance, capable of bearing the fire, is heated to a certain 
point, it emits light, the character of which depends upon the temperature. 
Thus, a bar of platinum or a piece of porcelain raised to a particular tempe- 
rature, become what is called red-hot, or emissive of red light ; at a higher 
degree of heat this light becomes whiter and more intense, and when urged 
to the utmost, as in the case of a piece of lime placed in the flame of the oxy- 
hydrogen blowpipe, the light becomes exceedingly powerful and acquires a 
tint of violet. Bodies in these states are said to be incandescent or ignited. 

Again, if the same experiment be made on a piece of charcoal, similar 
effeets will be observed, but something in addition; for whereas the platinum 
or porcelain, when removed from the fire, or the lime from the blow-pipe 
flame, begin immediately to cool, and emit less and less light, until they 
become completely obscure, the charcoal maintains to a great extent its high 
temperature. Unlike the other bodies too, which suffer no change whatever 
either of weight or substance, the charcoal gradually wastes away until it 

£450,000, and the consumption of coal in the same period to 180.000 tons, 1,460 millions of 
cubic feet of gas being made in the year. There were 134.:J00 private lights, ami 30,400 street 
lamps. 890 tons of coal were used in the retorts in the space of twenty-four Lours at mid- 
winter, and 7,120,000 cubic feet of gas consumed in the longest night. — Dr. Ure, Dictionary 
of Arts and Manufactures. Since that time the production of gas has been very considerably 
Increased. 

1 These bodies increase the illuminating power, and confer on the gas its peculiar odour. 



THE STRUCTURE OF FLAME. 



157 



disappears. This is what is called combustion in contradistinction to mere 
ignition ; the charcoal burns, and its temperature is kept up by the heat 
evolved in the act of union with the oxygen of the air. 

In the most general sense, a body in a state of combustion is one in the 
act of undergoing intense chemical action : any chemical action whatsoever, 
if its energy rise sufficiently high, may produce the phenomenon of com- 
bustion, by heating the body to such an extent that it becomes luminous. 

In all ordinary cases of combustion, the action lies between the burning 
body and the oxygen of the air ; and since the materials employed for the 
economical production of heat and light consist of carbon chiefly, or that 
substance conjoined with a certain proportion of hydrogen and oxygen, all 
common effects of this nature are cases of the rapid and violent oxidation 
of carbon and hydrogen by the aid of the free oxygen of the air. The heat 
must be referred to the act of chemical union, and the light to the elevated 
temperature. 

By this principle it is easy to understand the means which must be adopted 
to increase the heat of ordinary fires to the point necessary to melt refrac- 
tory metals, and to bring about certain desired effects of chemical decom- 
position. If the rate of consumption of the fuel can be increased by a more 
rapid introduction of air into the burning mass, the intensity of the heat 
will of necessity rise in the same ratio, there being reason to believe that the 
quantity of heat evolved is fixed and definite for the same constant quantity 
of chemical action. This increased supply of air may be effected by two 
distinct methods ; it may be forced into the fire by bellows or blowing- 
machines, as in the common forge, and in the blast and cupola-furnaces of 
the iron-worker, or it may be drawn through the burning materials by the 
help of a tall chimney, the fire-place being closed on all sides, and no en- 
trance of air allowed, save between the bars of the grate. Such is the kind 
of furnace generally employed by the scientific chemist in assaying and in 
the reduction of metallic oxides by charcoal ; the principle will be at once 
understood by the aid of the sectional drawing, in which a crucible is repre- 
sented, arranged in the fire for an operation of the kind mentioned. 
(Fig. 111.) 

Fig. 112. 





158 COMBUSTION, AND 

The " reverberatory" furnace (fig. 112) is one very much used in the arts 
"when substances are to be exposed to heat without contact with the fuel. 
The fire-chamber is separated from the bed or hearth of the furnace by a 
low wall or bridge of brick-work, and the flame and heated air are reflected 
downwards by the arched form of the roof. Any degree of heat can be ob- 
tained in a furnace of this kind, from the temperature of dull redness, to 
that required to melt very large quantities of cast-iron. The fire is urged 
by a chimney provided with a sliding-plate or damper to regulate the draught. 
Solids and liquids, as melted metal, enjoy, when sufficiently heated, the 
faculty of emitting light; the same power is possessed by gaseous bodies, 
but the temperature required to render a gas luminous is incomparably 
higher than in the cases already described. Gas or vapour in this condition 
constitutes flame, the actual temperature of which generally exceeds that of 
the white heat of solid bodies. 

The light emitted from pure flame is exceedingly feehle ; illuminating 
power is almost entirely dependent upon the presence of solid matter. The 
flame of hydrogen, or of the mixed gases, is scarcely visible in full daylight ; 
in a dusty atmosphere, however, it becomes much more luminous by igniting 
to intense whiteness the floating particles with which it comes in contact. The 
piece of lime in the blowpipe flame cannot have a higher temperature than 
that of the flame itself; yet the light it throws off is infinitely greater. 

Flames burning in the air, and not supplied with oxygen 
Pig. 113. from another source, are, as already stated, hollow; the che- 

mical action is necessarily confined to the spot where the two 
bodies unite. That of a lamp or candle, when carefully ex- 
■C a mined, is seen to consist of three separate portions. The 
dark central part, a, fig. 113, easily rendered evident by de- 
--B pressing upon the flame a piece of fine wire-gauze, consists of 
combustible matter drawn up by the capillarity of the wick, 
--A and volatilized by the heat. This is surrounded by a highly 
jJJ luminous cone or envelope, b, which, in contact with a cold 

body, deposits soot. On the outside a second cone, c, is to 
be traced, feeble in its light-giving power, but having an 
exceedingly high temperature. The explanation of these ap- 
pearances is easy : carbon and hydrogen are very unequal in 
their attraction for oxygen, the latter greatly exceeding the former in this 
respect ; consequently, when both are present, and the supply of oxygen 
limited, the hydrogen takes all, to the exclusion of a great part of the car- 
bon. Now this happens in the case under consideration, at some little dis- 
tance within the outer surface of the flame, namely, in the luminous portion ; 
the little oxygen which has penetrated thus far inwards is entirely consumed 
by the hydrogen, and the particles of deposited charcoal, which Avould, were 
they cooler, form smoke, become intensely ignited by the burning hydrogen, 
and evolve a light whose whiteness marks a very elevated temperature. In 
the exterior and scarcely visible cone, these particles of carbon undergo 
combustion. 

A jet of coal-gas exhibits these phenomena ; but, if the gas be previously 
mingled with air, or if air be forcibly mixed with, or driven into the flame, 
no such separation of carbon occurs, the hydrogen and carbon burn together, 
and the illuminating power almost disappears. 

The common mouth blowpipe is a little instrument of high utility ; it is 
merely a brass tube, fitted with an. ivory mouth-piece, and terminated by a 
jet, having a small aperture by which a current of air is driven across the 
flame of a candle. The best form is perhaps that contrived by Mr. Pepys, 
and shown in fig. 111. The flame so produced is very peculiar. 

Instead of the double envelope just described, two long pointed cones are 



THE STRUCTURE OF FLAME. 



159 



observed, which, when the blowpipe is good, and 
the aperture smooth and round, are very well de- 
fined, the outer one being yellowish, and the inner 
blue. Fig. 115. A double combustion is, in fact, 
going on, by the blast in the inside, and by the 
external air. The space between the inner and 
outer cones is filled with exceedingly hot com- 
bustible matter, possessing strong reducing or 
deoxidizing powers, while the highly heated air 
just beyond the point of the exterior cone ox- 
idizes with great facility. . A small portion of 
matter, supported on a piece of charcoal, or 
fixed in a ring at the end of a fine platinum 
wire, can thus in an instant be exposed to a very 
high degree of heat under these contrasted cir- 
cumstances, and observations of great value made 
in a very short time. The use of the instrument 
requires an even and uninterrupted blast of 
some duration, by a method easily acquired with 
a little patience ; it consists in employing for 
the purpose the muscles of the cheeks alone, 
respiration being conducted through the nostrils, 
and the mouth from time to time replenished 
with air without intermission of the blast. 

The Argand lamp, adapted to burn either oil 
or spirit, but especially the latter, is a very 
useful piece of chemical apparatus. In this 
lamp the wick is cylindrical, the flame being 
supplied with air both inside and outside ; the 
combustion is greatly aided by the chimney, 
which is made of copper when the lamp is used 
as a source of heat. Fig. 116 exhibits, in sec- 
tion, an excellent lamp of this kind for burning 
alcohol or wood-spirit. It is constructed of thin 
copper, and furnished with ground caps to the 
wick-holder and aperture ' by which the spirit is 
introduced, in order to prevent loss when the 
lamp is not in use. Glass spirit-lamps, fitted 



Fig. 114. 




Fig. 115. 




Fig. 116. 



Fig. 117. 





1 "When in use this aperture must always he opeu, otherwise an accident is pure to happen, 
the heat expands the air in the lamp, and the spirit is forced out in a state of inflammation. 



160 



COMBUSTION, AND 




with caps (fig. 117) to prevent evaporation, are very convenient for occa- 
sional use, being always ready and in order. 1 

In London, and other large towns where coal-gas is to be had, that sub- 
stance is constantly used with the greatest economy and advantage in every 
respect as a source of heat. Retorts, flasks, capsules, 
and other vessels, can be thus exposed to an easily re- 
gulated and invariable temperature for many successive 
hours. Small platinum crucibles may be ignited to 
redness by placing them over the flame on a little wire 
triangle. The arrangement shown in fig. 119, consist- 
ing of a common Argand gas-burner fixed on a heavy 
and low foot, and connected with a flexible tube of 
caoutchouc or other material, leaves nothing to desire. 

The kindling-point, or temperature at which combus- 
tion commences, is very different with different substan- 
ces ; phosphorus will sometimes take fire in the hand ; 
sulphur requires a temperature exceeding that of boil- 
ing water ; charcoal must be heated to redness. Among 
gaseous bodies the same fact is observed : hydrogen is 
inflamed by a red-hot wire ; carbonetted hydrogen re- 
quires a white heat to effect the same thing. When flame 
is cooled by any means below the temperature at which the rapid oxidation 
of the combustible gas occurs, it is at once extinguished. Upon this depends 
the principle of Sir H. Davy's invaluable safe-lamp. 

Mention has already been made of the frequent disengagement of great 
quantities of light carbonetted hydrogen gas in coal-mines. This gas, mixed 
with seven or eight times its volume of atmospheric air, becomes highly ex- 
plosive, taking fire at a light, and burning with a pale blue flame ; and many 
fearful accidents have occurred from the ignition of large quantities of 
mixed air and gas occupying the extensive galleries and workings of a 
mine. Sir H. Dawy undertook an investigation with a view to discover some 
remedy for this constantly-occurring calamity; his labours resulted in some 
exceedingly important discoveries respecting flame, of which the substance 
has been given, and which led to the construction of the lamp which bears 
his name. 

When two vessels filled with a gaseous explosive mixture are connected by 
a narrow tube, and the contents of one fired by the electric spark, or other- 
wise, the flame is not communicated to the other, provided the diameter of 
the tube, its length, and the conducting power for heat of its material, bear 
a certain proportion to each other ; the flame is extinguished by cooling, and 
its transmission rendered impossible. 

In this experiment, high conducting power and diminished diameter com- 
pensate for diminution of length ; and to such an extent can this be carried, 



Fig. 118. 




1 The spirit-lamp represented in nor. 118, is 
one contrived by Dr. Mitchell. "It is made 
of tinned iron. The alcohol is poured out by 
means of the hollow handle, and is admitted 
to the cylindrical burner by two or three 
tubes which are placed at the very bottom of 
the fountain. By such an arrangement of 
parts, the alcohol may be added as it is con- 
sumed, and the flame kept uniform.; and as 
the pipes which pass to the burner are so re- 
mole from the flame, the alcohol never be- 
comes heated so as to fly off through the 
vent-hole, and thus to cause greater waste 
and danger of explosion." 

A cylindrical chimney is an advantageous 
addition for many purposes. It may be made 
of tin-plate or copper. — R. B. 



THE STRUCTURE OF FLA. ME, 



161 



Fig. 120. 



that metallic gauze, which may be looked upon as a series of very short 
square tubes arranged side by side, arrests in the most complete manner the 
passage of flame in explosive mixtures, when of sufficient 
degree of fineness, depending upon the inflammability of the 
gas. Most providentially, the fire-damp mixture has an ex- 
ceedingly high kindling point ; a red heat does not cause in- 
flammation ; consequently, the gauze will be safe for this 
substance, when flame would pass in almost any other case. 

The miner's safe-lamp (fig. 120) is merely an ordinary oil- 
lamp, the flame of which is enclosed in a cage of wire gauze ; 
made double at the upper part, containing about 400 aper- 
tures to the square inch. The tube for supplying oil to the 
reservoir reaches nearly to the bottom of the latter, while the 
wick admits of being trimmed by a bent wire passing with 
friction through a small tube in the body of the lamp ; the 
flame can thus be kept burning for any length of time, with- 
out the necessity of unscrewing the cage. When this lamp is 
taken into an explosive atmosphere, although the fire-damp 
may burn within the cage with such energy as sometimes 
to heat the metallic tissue to dull redness, the flame is not 
communicated to the mixture on the outside. 

These effects may be conveniently studied by suspending 
the lamp in a large glass jar, and gradually admitting coal- 
gas below. The oil-flame is at first elongated, and then, as 
the proportion of gas increases, extinguished, while the in- 
terior of the gauze cylinder becomes filled with the burn- 
ing mixture of gas and air. As the atmosphere becomes 
purer, the wick is once more relighted. These appear- 
ances are so remarkable, that the lamp becomes an admi- 
rable indicator of the state of the air in different parts of 
the mine. 1 

The same great principle has been ingeniously applied 
by Mr. Hemming to the construction of the oxy-hydrogen 
safety-jet formerly mentioned. This is a tube of brass 
about four inches long, filled with straight pieces of fine 
brass wire, the whole being tightly wedged together by a 
pointed rod, forcibly driven into the centre of the bundle. 
Fig. 121. The arrangement thus presents a series of 
metal tubes, very long in proportion to their diameter, the 
cooling powers of which are so great as to prevent the pos- 
sibility of the passage of flame, even with oxygen and hy- 
drogen. The jet may be used, as before mentioned, with 
a common bladder, without a chance of explosion. The 
fundamental fact of flame being extinguished by contact 
with a cold bod} r , may be elegantly shown by twisting a 
copper wire (fig. 122) into a short spiral, about 0-1 inch 

Fig. 122. 



Fig. 121. 




1 This is the true use of the lamp, namely, to permit the viewer or superintendent, with 
ont risk to himself, to examine the state of the air in every part of the mine; not to enable- 
workmen to continue their labours in an atmosphere habitually explosive, which must be 
unfit for human respiration, although the evil effects may be slow to appear. Owners of 
coal-mines should be compelled either to adopt efficient means of ventilation, or to clos* 
workings of this dangerous character altogether. 

14* 



162 NITROGEN AND HYDROGEN; AMMONIA. 

in diameter, and then passing it cold over the flame of a wax candle ; the 
latter is extinguished. If the spiral be now heated to redness by a spirit- 
lamp, and the experiment repeated, no such effect follows. 1 

NITROGEN AND HYDROGEN ; AMMONIA. 

When powdered sal-ammoniac is mixed with moist hydrate of lime, and 
gently heated in a glass flask, a large quantity of gaseous matter is disengaged, 
which must be collected over mercury, or by displacement, advantage being 
taken of its low specific gravity. 

Ammoniacal gas thus obtained is colourless ; it has a very powerful pun- 
gent odour, and a strong alkaline reaction to test-paper, by which it may be 
at once distinguished from nearly all other bodies possessing the same physi- 
cal characters. Under a pressure of 6-5 atmospheres at 60° (15° -5C), am- 
monia condenses to the liquid form. 3 Water dissolves about 700 times its 
volume of this remarkable gas. forming a solution which in a more dilute 
state has long been known under the name of liquor ammoniaz; by heaf, : a 
great part is again expelled. The solution is decomposed by chlorine, sal-, 
ammoniac being formed, and nitrogen set free. 

Ammonia has a density of 0-589; 100 cubic inches weigh 18-26 grains. 
It cannot be formed by the direct union of its elements, although it is some- 
times produced under rather remarkable circumstances by the deoxidation 
of nitric acid. The great sources of ammonia are the feebly-compounded 
azotized principles of the animal and vegetable kingdoms, which, when left 
to putrefactive change, or subjected to destructive distillation, almost inva- 
riably give rise to an abundant production of this substance. 

The analysis of ammoniacal gas is easily effected. When a portion is con- 
fined in a graduated tube over mercury, and electric sparks passed through 
it for a considerable time, the volume of the gas gradually increases until it 
becomes doubled. On examination, the tube is found to contain a mixture 
of 3 measures hydrogen gas, and 1 measure nitrogen. Every two volumes 
of the ammonia, therefore, contained three volumes of hydrogen and one of 
nitrogen, the whole being condensed to the extent of one-half. The weight 
of the two constituents will be in the proportion of 3 parts hydrogen to 14 
parts nitrogen. 

Ammonia may also be decomposed into its elements by transmission 
through a red-hot tube. 

Solution of ammonia is a very valuable reagent, and is employed in a great 
number of chemical operations, for some of which it is necessary to have it 
perfectly pure. The best mode of preparation is the following : — 

Equal weights of sal-ammoniac and quicklime are taken ; the lime is slaked 
in a covered basin, and the salt reduced to powder. These are mixed, and 
introduced into the flask employed in preparing solution of hydrochloric 
acid, together with just enough water to damp the mixture, and cause it to 
aggregate into lumps ; the rest of the apparatus is arranged exactly as in 

1 "Where coal-gas is to be had. it may be advantageously used as a source of heat, by taking 
advantage of the above-mentioned fact. On passing a current of gas through a vide vertical 
tube, open at the bottom to afford a free mixture with atmospheric air. but closed at the top 
by wire gauze, and then kindling the mixture after its escape through the meshes, it will 
burn with feeble illuminating power, but no loss of heat. 'When the proportion of the gas 
to the atmospheric air is such as not to allow the Same to become yellow, the combust ion 
will be complete, and no carbonaceous deposit will he formed on cold bodies held over the 
tames. The length and diameter of the cylinder are determined ly the amount of gas to be 
burnt, and the length maybe much decreased by interposing a second diaphragm of wire 
gauze about mid-length of the cylinder, the current of gas being introduced below this, by 
which means a more thorough and rapid mixture is made with the atmospheric air. — Sir 
John Robinson, K. II. &c, Ed. New Phil. Journal, 1840.— II. B. 

9 .At the temperature of — 103° ( — 75°C), liquid ammonia freezes into a colourless solid, 
hw<tvier than the liquid itself. — (Faraday.)— -B. 13. 



NITROGEN AND BORON. 163 

the former case, with an ounce or two of water in the wash-bottle, or enough 
to cover the ends of the tubes, and the gas conducted afterwards into pure 
distilled water, artificially cooled, as before. The cork-joints are made tight 
with was, a little water is put into the safety-funnel, heat cautiously applied 
to the flask, and the whole left to itself. The disengagement of ammonia is 
very regular and uniform. Chloride of calcium, with excess of hydrate of 
lime, remains in the flask. 1 

The decomposition of the salt is usually represented in the manner shown 
by the subjoined diagram. 

{Ammonia Ammonia. 
Hydrochloric $ Hydrogen — ^-» Water, 
acid l Chlorine. 



Lime. (Oxygen- 

\ Calcium- 




Chloride of 
calcium. 



Solution of ammonia should be perfectly colourless, leave no residue on 
evaporation, and when supersaturated by nitric acid, give no cloud or mud- 
diness with nitrate of silver. Its density diminishes with its strength, that 
of the most concentrated being about 0-875 ; the value in alkali of any 
sample of liquor ammonite is most safely inferred, not from a knowledge 
of its density, but from the quantity of acid a given amount will saturate. 
The mode of conducting this experiment will be found described under 
Alkalimetry. 

When solution of ammonia is mixed with acids of various kinds, salts are 
generated, which resemble in the most complete manner the corresponding 
compounds of potassa and soda ; these are best discussed in connexion with 
the latter. Any ammoniacal salt can at once be recognized by the evolution 
of ammonia when it is heated with hydrate of lime, or solution of carbonate 
of potassa or soda. 

NITROGEN AND BORON. 

A combination of nitrogen with boron was first obtained by Balmain. 
Woehler prepared it by mixing one part of pure dry borax with two parts of 
dry sal-ammoniac, heating to redness, boiling with water and hydrochloric 
acid, filtering and washing with hot water, when the compound remained in 
the form of a white powder. As yet it has not been obtained quite free 
from oxygen. 

SULPHUR, SELENIUM, AND PHOSPHORUS, WITH HYDROGEN. 

Sulphuretted Hydrogen ; Hydrosxdphuric Acid. — There are two methods by 
which this important compound can be readily prepared, namely, by the 
action of dilute sulphuric acid upon sulphide of iron, and by the decomposi- 
tion of sulphide of antimony by hydrochloric acid. The first method yields 
it most easily, and the second in the purest state. 

Protosulphide of iron is put into the apparatus for hydrogen, already 
several times mentioned, together with some water, and oil of vitriol is added 
by the funnel, until a copious disengagement of gas takes place. This is to 
be collected over tepid water. The reaction is thus explained : — 

1 See Fig. 106, p. 1 12. 



J 64 



SULPHUR WITH HYDROGEN. 



Sulphide of iron { ^ hur 




"Water 



Sulphuric acid 



Sulphuretted hydrogen. 



Sulphate of protoxide of iron. 



By the other plan, finely-powdered sulphide of antimony is put into a flask, 
to which a cork and bent tube can be adapted, and strong liquid hydro- 
chloric acid poured upon it. On the application of heat, a double inter- 
change occurs between the bodies present, sulphuretted hydrogen being 
formed, and chloride of antimony. The action only lasts while the heat is 
maintained. 



Hydrochloric acid { ^TinT" 

Sulphur 



Sulphuretted hydrogen. 



Sulphide of antimony 



Antimony • 



-Chloride of antimony. 



Fig. 123. 



Sulphuretted hydrogen is a colourless gas, having the odour of putrid 
eggs ; it is most offensive when in small quantity, when a mere trace is pre- 
sent in the air. It is not irritating, but, on the contrary, powerfully narcotic. 
When set on fire, it burns with a blue flame, producing water and sulphurous 
acid when the supply of air is abundant ; and depositing sulphur when the 
oxygen is deficient. Mixed with chlorine, it is instantly decomposed, with 
separation of the whole of the sulphur. 

This gas has a specific gravity of 1*171 ; 100 cubic inches weigh 36-33 
grains. 

A pressure of 17 atmospheres at 50° (10°C) reduces 
it to the liquid form. Cold water dissolves its own 
volume of sulphuretted hydrogen, and the solution 
is often directed to be kept as a test ; it is so prone 
to decomposition, however, by the oxygen of the air, 
that it speedily spoils. A much better plan is to keep 
a little apparatus for generating the gas always at 
hand, and ready for use at a moment's notice. A small 
bottle or flask (fig. 123), to which a bit of bent tube is 
fitted by a cork, is supplied with a little sulphide of 
iron and water ; when required for use, a few drops 
of oil of vitriol are added, and the gas is at once 
evolved. The experiment completed, the liquid is 
poured from the bottle, replaced by a little clean water, 
and the instrument is again ready for use. 

When potassium is heated in sulphuretted hydrogen, the metal burns with 
great energy, becoming converted into sulphide, while pure hj'drogen remains, 
equal in volume to the original gas. Taking this fact into account, and 
comparing the density of the gas with those of hydrogen and sulphur-vapour, 
it appears that every volume of sulphuretted hydrogen contains one volume 
of hydrogen and one-sixth of a volume of sulphur-vapour, the whole con- 
densed into one volume. This corresponds very nearly with its composition 
by weight, determined by other means, namely, 16 parts sulphur and 1 part 
hydrogen. 

When a mixture is made of 100 measures of sulphuretted hydrogen and 
150 measures of pure oxygen, and exploded by the electric spark, complete 
combustion ensues, ana 100 measures of sulphurous acid gas result. 

Sulphuretted hydrogen is a frequent product of the putrefaction of organic 
matter, both animal and vegetable ; it occurs also in certain mineral springs, 
as at Harrowgatc, and elsewhere. When accidentally present in the atmo- 




PERSULPHIDE OF HYDROGEN. 165 

sphere of an apartment, it may be instantaneously destroyed by a small 
quantity of chlorine gas. 

There are few reagents of greater value to the practical chemist than this 
substance ; when brought in contact with many metallic solutions, it gives 
rise to precipitates, which are often exceedingly characteristic in appearance, 
and it frequently affords the means also of separating metals from each other 
with the greatest precision and certainty. The precipitates spoken of are 
insoluble sulphides, formed by the mutual decomposition of the metallic 
oxides or chlorides and sulphuretted hydrogen, water or hydrochloric acid 
being produced at the same time. All the metals are, in fact, precipitated 
whose sulphides are insoluble in water and in dilute acids. 

Sulphuretted hydrogen possesses itself the properties of an acid; its 
solution in water reddens litmus paper. 

The best test for the presence of this compound is paper wetted with 
solution of acetate of lead. This salt is blackened by the smallest trace of 
the gas. 

Persulphide of Hydrogen. — This substance corresponds in constitution 
and instability to the binoxide of hydrogen ; it is prepared by the following 
means : — 

Equal weights of slaked lime and flowers of sulphur are boiled with 5 or 
6 parts of water for half an hour, when a deep orange-coloured solution is 
produced, containing among other things persulphide of calcium. This is 
filtered, and slowly added to an excess of dilute sulphuric acid, with constant 
agitation. A white precipitate of separated sulphur and sulphate of lime 
makes its appearance, together with a quantity of yellow oily -looking 
matter, which collects at the bottom of the vessel ; this is persulphide of 
hydrogen. 1 

If the experiment be conducted by pouring the acid into the solution of 
sulphide, then nothing but finely-divided precipitated sulphur is obtained. 

The persulphide is a yellow, viscid, insoluble liquid, exhaling the odour 
of sulphuretted hydrogen; its specific gravity is 1-769. It is slowly decom- 
posed even in the cold into sulphur and sulphuretted hydrogen, and instantly 
by a higher temperature, or by contact with many metallic oxides. This 
compound probably contains twice as much sulphur in relation to the other 
elements, as sulphuretted hydrogen. 

Hydrogen and Selenium; Selenietted Hydrogen. — This substance is produced 
by the action of dilute sulphuric acid upon selenide of potassium or iron ; 
it very much resembles sulphuretted hydrogen, being a colourless gas, freely 

1 The reaction which ensues when hydrate of lime, sulphur, and water, are hoiled together, 
is rather complex; bisulphide or pentasulphide of calcium being formed, together with hypo 
sulphite of lime, arising from the transfer of the oxygen of the decomposed lime to another 
portion of sulphur. 

2 en limp \ ^ e 1" ca ^ c * um _^ J » 2 eq. bisulphide of calcium. 

e( i- ume } 2 eq. oxygen 




4eq. sulphur- 

2 eq. sulphur ^=» 1 eq. hyposulphurous acid. 

The bisulphide of calcium, decomposed by an acid under favourable circumstances, yields 
salt of lime and bisulphide (persulphide) of hydrogen. 

... ,. ( 2 eq. sulphur _. 1 eq. bisulphide of hydrogen. 

1 eq. bisulp. calcium j ± £ c J [nm — 




leq. water j J eq. hydrogen 

* ( 1 eq. oxygen . 

Sulphuric acid _ZZ==S*- 1 e q. sulphate of lime, 

When the acid is poured into the sulnhide, sulphuretted hydrogen, water, and sulphate of 
lime, are produced, while the excess of sulphur is thrown down as a fine white powder, the 
" precipitated sulphur"' of the Pharmacopoeia. 'When the object is to prepare the latter sal* 
6lance, hydrochloric acid must be used in the place of sulphuric. 



1GG 



PHOSPHORUS WITH HYDROGEN. 



soluble in water, and decomposing metallic solutions like that subtance ; in- 
soluble selenides are thus produced. This gas is said to act very powerfully 
upon the lining membrane of the nose, exciting catarrhal symptoms, and 
destroying the sense of smell. It contains 89-5 parts selenium, and 1 part 
hydrogen. 

Phosphorus and Hydrogen ; Phosphoretled Hydrogen. — This body bears a 
slight analogy in some of its chemical relations to ammoniacal gas ; it is, 
however, destitute of alkaline properties. 

Phosphoretted hydrogen may be obtained in a state of purity by heating 
in a small retort hydrated phosphorous acid, which is by such treatment de- 
composed into phosphoretted hydrogen and hydrated phosphoric acid. 1 

Thus obtained, the gas has a density of 1-24. It contains 82 parts phos- 
phorus, and 3 parts hydrogen, and is so constituted that every two volumes 
contain 3 volumes of hydrogen and half a volume of phosphorus-vapour, 
condensed into two volumes. It possesses a highly disagreeable odour of 
garlic, is slightly soluble in water, and burns with a brilliant white flame, 
forming water and phosphoric acid. 

Phosphoretted hydrogen may also be produced by boiling together in a 
retort of small dimensions caustic potassa or hydrate of lime, water, and 
phosphorus ; the vessel should be filled to the neck, and the extremity of 
the latter made to dip into the water of the pneumatic trough. In the reaction 
which ensues the water is decomposed, and both its elements combine with 
the phosphorus. The alkali acts by its presence determining the decomposition 
of the water, in the same manner as sulphuric acid determines the decompo- 
sition of water when in contact with zinc. 



Water ...{Hydrogen 
\ Oxygen 



Phosphorus 
Phosphorus 
Lime 




Phosphoretted hydrogen. 



Hypophosphite of lime. 



The phosphoretted hydrogen prepared by the latter process has the sin- 
gular property of spontaneous inflammability when admitted into the air or 
into oxygen gas; with the latter, the experiment is very beautiful, but re- 
quires caution ; the bubbles should be singly admitted. When kept over 
water for some time, the gas loses this property, without otherwise suffering 
any appreciable change : but if dried by chloride of calcium, it may be kept 
unaltered for a much longer period. M. Paul Thenard has shown that the 
spontaneous combustibility of the gas arises from the presence of the vapour 
of a liquid phosphide of hydrogen, which can be procured in small quantity, 
by conveying the gas produced by the action of the water on phosphide of 
calcium through a tube cooled by a freezing mixture. This substance forms 
a colourless liquid of high refractive power and very great volatility. It does 
not freeze at 0° ( — 17°-8C). In contact with air it inflames instantly, and 
its vapour in very small quantity communicates spontaneous inflammability 
to pure phosphoretted hydrogen, and to all other combustible gases. It is 
decomposed by light into gaseous phosphoretted hydrogen, and a solid phos- 
phide which is often seen on the inside of jars containing gas which has lost 



Decomposition of hydrated phosphorous acid by heat: — 





4eq. _ 
real acid 


f 1 eq. phosph. 


i oq. hydrated 


3 eq. phosph. 

12 eq. oxyp;en 


phosphorous J 




3 eq. hydros. 


acid. 


12 eq. 


9 eq, hydrog. 




water 


3 eq. oxygen 






L 9 eq.. oxygen 




1 eq. phosphoretted hydrogen, PII3 



9 eq. Mater. J P^nc acid. 



NITROGEN WITH CLTLORINE, ETC. 167 

the property of spontaneous inflammation by exposure to light. Strong 
acids occasion its instantaneous decomposition. Its instability is equal to 
that of binoxide of hydrogen. It is to be observed that the pure phospho- 
retted hydrogen gas itself becomes spontaneously inflammable if heated to 
the temperature of boiling water. 1 

Phosphoretted hydrogen decomposes several metallic solutions, giving rise 
to precipitates of insoluble phosphides. With hydriodic acid it forms a crys- 
talline compound somewhat resembling sal-ammoniac. 

NITROGEN WITH CHLORINE AND IODINE. 

Chloride of Nitrogen. — When sal-ammoniac or nitrate of ammonia is dis- 
solved in water, and ajar of chlorine gas inverted into the solution, the gas 
is absorbed, and a deep yellow oily liquid is observed to collect upon the 
surface of the solution, which ultimately sinks in globules to the bottom. 
This is chloride of nitrogen, the most dangerously-explosive substance known. 
The following is the safest method of conducting the experiment: — 

A somewhat dilute and tepid solution of pure sal-ammoniac in distilled 
water is poured into a clean basin, and a bottle of chlorine, the neck of 
which is quite free from grease, inverted into it. A shallow and heavy leaden 
cup is placed beneath the mouth of the bottle to collect the product. When 
enough has been obtained, the leaden vessel may be withdrawn with its dan- 
gerous contents, the chloride remaining covered with a stratum of water. 
The operator should protect his face with a strong wire-gauze mask when 
experimenting upon this substance. 

The change is explained by the following diagram :- 

Chlorine ^^^ Chloride of nitrogen. 

Chlorine- ^^ ^^^ Hydrochloric acid 

{\ Nitrogen 
\ Hydrogen 
Hydrochloric acid — — Hydrochloric acid. 

Chloride of nitrogen is very volatile, and its vapour is exceedingly irrita- 
ting to the eyes. It has a specific gravity of 1-653. It may be distilled at 
160° (71°-1C), although the experiment is attended with great danger., 
Between 200° (93°-3C) and 212° (100°C) it explodes with the most fearful 
violence. Contact with almost any combustible matter, as oil or fat of any 
kind, determines the explosion at common temperatures ; a vessel of porce- 
lain, glass, or even of cast-iron, is broken to pieces, and the leaden cup 
receives a deep indentation. This body has usually been supposed to contain 
nitrogen and chlorine in the proportion of 14 parts of the former to 106-5 
parts of the latter, but recent experiments upon the corresponding iodine- 
compound induce a belief that it contains hydrogen. 2 

Iodide of Nitrogen. — When finely-powdered iodine is put into caustic am- 
monia it is in part dissolved, giving a deep brown solution, and the residue 
is converted into a black powder, which is the substance in question. The 
brown liquid consists of hydriodic acid holding iodine in solution, and is 
easily separated from the solid product by a filter. The latter while still 
wet is distributed in small quantities upon separate pieces of bibulous paper, 
and left to dry in the air. 

Iodide of nitrogen is a black insoluble powder, which, when dry, explodes 
with the slightest touch, even that of a feather; and sometimes without any 
obvious cause. The explosion is not nearly so violent as that of the com- 

x Ann. Cbim. et Phys. 3rd series, xiv. 5. According to M. Thenard, the new liquid phosphide 
of hydrogen contains PII2 and the solid P2H. The gas is represented by the formula PJI.3. 
3 Instead of NCI3, it may in reality he Nil CI2. 



168 OTHER COMPOUNDS OF 

pound \ast described, and is attended with the production of violent fumes 
of iodine. Dr. Gladstone has proved that this substance contains hydrogen, 
and that it may be viewed as ammonia, in which two-thirds of the hydrogen 
are replaced by iodine. 

OTHER COMPOUNDS OF NON-METALLIC ELEMENTS. 

Chlorine tvith Sulphur and Phosphorus. — Chloride of Sulphur. — The subchlo- 
ride is easily prepared by passing dry chlorine over the surface of sulphur 
kept melted in a small glass retort connected with a good condensing ar- 
rangement. The chloride distils over as a deep orange-yellow mobile liquid, 
of peculiar and disagreeable odour, which boils at 280° (137° -8C). As this 
substance dissolves both sulphur and chlorine, it is not easy to obtain it in a 
pure and definite state. It contains 32 parts sulphur and 35-5 chlorine. 1 

Subchloride of sulphur is instantly decomposed by water ; hydrochloric 
and hyposulphurous acids are formed, and sulphur separated. The hypo- 
sulphurous acid in its turn decomposes into sulphur and sulphurous acid. 

Protochloride of sulphur is formed by exposing the above compound for a 
considerable time to the action of chlorine, and then distilling it in a stream 
of the gas. % It has a deep red colour, is heavier than water, boils at 147° 
(63°-9C), and contains twice as much chlorine as the subchloride. 2 

Chlorides of Phosphorus. — Terchloride. 3 — This is prepared in the same man- 
ner as subchloride of sulphur, by gently heating phosphorus in dry chlorine 
gas, the phosphorus being in excess. Or, by passing the vapour of phos- 
phorus over fragments of calomel (subchloride of mercury) contained in a 
glass tube and strongly heated. It is a colourless, thin liquid, which fumes 
in the air, and possesses a powerful and offensive odour. Its specific gravity 
is 1-45. Thrown into water, it sinks to the bottom of that liquid, and be- 
comes slowly decomposed, yielding phosphorous acid and hydrochloric acid. 
This compound contains 32 parts phosphorus, and 106-5 parts chlorine. 

Pentachloride of Phosphorus. 11 — The compound formed when phosphorus is 
burned in excess of chlorine. Into a large retort, fitted with a cap and stop- 
cock, pieces of phosphorus are introduced ; the retort is then exhausted, and 
filled with dry chlorine gas. The phosphorus takes fire, and burns with a 
pale flame, forming a white, volatile, crystalline sublimate, which is il\e pen- 
tachloride. It may be obtained in larger quantity by passing a stream of 
chlorine gas into the preceding liquid terchloride, which becomes gradually 
converted into a solid, crystalline mass. Pentachloride of phosphorus is 
decomposed by water, yielding phosphoric and hydrochloric acids. 

Two bromides of phosphorus are known, closely corresponding in proper- 
ties and constitution with the chlorides. Several compounds of iodine and 
phosphorus appear to exist : they are fusible crystalline substances, which 
decompose by contact with water, and yield hydriodic and phosphorous, or 
phosphoric acid. 

Chlorine and Carbon. — Several compounds of chlorine and carbon are 
known. They are obtained indirectly by the action of chlorine upon certain 
organic compounds, and are described in connection with the history of 
alcohol, &c. 

Iodine tvith Sulphur and Phosphorus. — These compounds are formed by 
gently heating together the materials in vessels from which the air is ex- 
cluded. They present few points of interest. 

Chlorine with Iodine. — Iodine readily absorbs chlorine gas, forming, when 
the cnlorine is in excess, a solid, yellow compound, and when the iodine pre- 
ponderates, a brown liquid. The solid iodide is decomposed by water, yield- 
ing hydrochloric and iodic acids. 6 

*S 2 C1. 3 SC1. 3 PC1 3 . «PC1 5 . 

« Hence it doubtless contains 1 eq. iodine, and 5 eq chlorine, or ICle. 



NON-METALLIC ELEMENTS. 169 

Another definite compound is formed by heating in a retort a mixture of 
1 part iodine, and 4 parts chlorate of potassa ; oxygen-gas and chloride of 
iodine are disengaged, and the latter may be condensed by suitable means. 
Iodate and perchlorate of potassa remain in the retort. 

This chloride of iodine is a yellow, oily liquid, of suffocating smell and 
astringent taste ; it is soluble in water and alcohol without decomposition. 
It probably consists of 127 parts iodine, and 35-5 parts chlorine. 1 

Carbon and Sulphur. — Bisulphide of Carbon. — A wide porcelain tube is 
filled with pieces of charcoal, which have been recently heated to redness in a 
covered crucible, and fixed across a furnace in a slightly inclined position. 
Into the lower extremity a tolerably wide tube is secured by the aid of a 
cork ; this tube bends downwards, and passes nearly to the bottom of a bottle 
filled with fragments of ice and a little water. The porcelain tube being 
heated to a bright redness, fragments of sulphur are thrown into the open 
end, which is immediately afterwards stopped by a cork. The sulphur 
melts, and becomes converted into vapour, which, at that high temperature, 
combines with the carbon, forming an exceedingly volatile compound, which 
is condensed by the ice and collects at the bottom of the vessel. This is 
collected and re-distilled with very gentle heat in a retort connected with a 
good condenser. Bisulphide of carbon is a transparent colourless liquid of 
great refractive and dispersive power. Its density is 1-272. It boils at 110° 
(43°-3C), and emits vapour of considerable elasticity at common temper- 
atures. The odour of this substance is very repulsive. When set on fire in 
the air it burns with a blue flame, forming carbonic acid and sulphurous 
acid gases ; and when its vapour is mixed with oxygen it becomes explosive. 

It freely dissolves sulphur, and by spontaneous evaporation deposits the 
latter in beautiful crystals ; it also dissolves phosphorus 

Chlorides of Silicium and Boron. — Both silicium and boron combine directly 
with chlorine. The chloride of silicium is most easily obtained by mixing 
finely-divided silica with charcoal-powder and oil, strongly heating the mix- 
ture in a covered crucible, and then exposing the mass so obtained in a por- 
celain tube, heated to full redness, to the action of perfectly dry chlorine 
gas. A good condensing arrangement, supplied with ice-cold water, must 
be connected with the porcelain tube. The product is a colourless and very 
volatile liquid, boiling at 122° (50°C), of pungent, suffocating odour. In 
contact with water it yields hydrochloric acid and gelatinous silica. This 
substance contains 21-3 parts silicium, and 106-5 chlorine. 3 

Bromide of Silicium may be obtained by a similar proceeding, the vapour 
of bromine being substituted for chlorine ; it resembles the chloride, but is 
less volatile. 

Chloride of Boron is a permanent gas, decomposed by water with produc- 
tion of boracic and hydrochloric acids, and fuming strongly in the air. It 
may be most easily obtained by exposing to the action of dry chlorine at a 
very high temperature an intimate mixture of glassy boracic acid and char- 
coal. It resembles in constitution chloride of silicium. 

1 Or single equivalents. a Or SiCl3. 



15 



170 GENERAL PRINCIPLES OP 



ON THE GENERAL PRINCIPLES OF CHEMICAL PHILOSOPHY. 



The study of the non-metallic elements can be pushed to a very consider 
able extent, and a large amount of precise and exceedingly important infor- 
mation acquired, without much direct reference to the great fundamental 
laws of chemical union; the subject cannot be discussed in this manner com- 
pletely, as will be obvious from occasional cases of anticipation in many of 
the foregoing foot-notes ; still, much may be done by this simple method of 
proceeding. The bodies themselves, in their combinations, furnish admirable 
illustrations of the general laws referred to, but the study of their leading 
characters and relations does not of necessity involve a previous knowledge 
of these laws themselves. 

It is thought that by such an arrangement the comprehension of these 
very important general principles may become in some measure facilitated 
by constant references to examples of combinations, the elements and pro- 
ducts of which have been already described. So much more difficult is it to 
gain a clear and distinct idea of any proposition of great generality from a 
simple enunciation, than to understand the bearing of the same law when 
illustrated by a single good and familiar instance. 

Before proceeding farther, however, it is absolutely necessary that these 
matters should be discussed ; the metallic compounds are so numerous and 
complicated, that the establishment of some general principle, some con- 
necting link, becomes indispensable. The doctrine of equivalents, and the 
laws which regulate the formation of saline compounds, supply this defi- 
ciency. 

In the organic department of the science, the most interesting perhaps of 
all, a knowledge of these principles, and, farther, an acquaintance or even 
familiarity with the beautiful system of chemical notation now in use, are 
absolutely required. This latter is found of very great service in the study 
of salts and other complex inorganic compounds, but in that of organic 
chemistry it cannot be dispensed with. 

It will be proper to commence with a notice of the principles which regu- 
late the modern nomenclature in use in chemical writings. 

NOMENCLATURE. 

In the early days of chemistry the arbitrary and fanciful names which 
were conferred by each experimenter on the new compounds he discovered 
sufficed to distinguish these from each other, and to render intelligible the 
description given of their production. Such terms as oil of vitriol, spirit of 
salt, oil of tartar, butter of antimony, sugar of lead, flowers of zinc, sal enixum, 
sal mirabile, &c, were then quite admissible. In process of time, however, 
when the number of known substances became vastly increased, the confu- 
sion of language produced by the want of a more systematic kind of nomen- 
clature became quite intolerable, and the evil was still farther increased by 
the frequent use of numerous synonyms to designate the same substance. 

In the year 1787, Lavoisier and his colleagues published the plan of the 



CHEMICAL PHILOSOPHY. 171 

remarkable system of nomenclature, which, with some important extensions 
since rendered necessary, has up to the present time to a great extent satisfied 
the wants of the science. It is in organic chemistry that the deficiencies of 
this plan are chiefly felt, and that something like a return to the old method 
has been rendered inevitable. Organic chemistry is an entirely new science 
which has sprung up since the death of these eminent men, and has to deal 
with bodies of a constitution or type differing completely from that of the 
inorganic acids, bases and salts which formed the subjects of the chemical 
studies of that period. The rapid progress of discover} 7 , by which new com- 
pounds, and new classes of compounds, often of the most unexpected nature, 
are continually brought to light, sufficiently proves that the time to attempt 
the construction of a permanent systematic plan of naming organic bodies 
has not yet arrived. 

The principle of the nomenclature in use may be thus explained : — Ele- 
mentary substances still receive arbitrary names, generally, but not always, 
referring to some marked peculiarity of the body ; an uniformity in the ter- 
mination of the word has generally been observed, as in the case of new 
metals whose names are made to end in item. 

Compounds formed by the union of non-metallic elements with metals, or 
with other non-metallic elements, are collected into groups having a kind of 
generic name derived from the non-metallic element, or that most opposed 
in characters to a metal, and made to. terminate in ide. 1 Thus we have 
oxides, chlorides, iodides, bromides, &c, of hydrogen and of the several 
metals ; oxides of chlorine ; chlorides of iodine and sulphur ; sulphides and 
phosphides of hydrogen and the metals. 

The nomenclature of oxides has been already described (p. 109). They 
are divided into three classes, namely, alkaline or basic oxides, neutral 
oxides, and oxides possessing acid characters. In practice the term oxido 
is usually restricted to bodies belonging to the first two groups, those of the 
third being simply called acids. Generally speaking, these acids are derived 
from the non-metallic elements, which yield no basic oxides ; many of the 
metals, however, yield acids of a more or less energetic description. 

The same element in combining with oxygen in more than one proportion 
may yield more than one acid ; in this case it has been usual to apply to the 
acid containing most oxygen the termination ic, and to the one containing 
the lesser quantity the termination ous. "When more members of the same 
group came to be known, recourse was had to a prefix, hypo or hyper, (or 
per,) signifying deficiency or excess. Thus, the two earliest known acids 
of sulphur were named respectively sulphurous and sulphuric acids ; subse- 
quently two more were discovered, the one containing less oxygen than 
sulphurous acid, the other intermediate in composition between sulphurous 
and sulphuric acids. These were called hypos ulphurous and hyposulphuric 
acids. The names of the new acids of sulphur of still more recent discovery 
are not yet permanently fixed ; Lavoisier's system, even in its extended form, 
fails to furnish names for such a lengthened series. Other examples of the 
nomenclature of acids with increasing proportions of oxygen are easily found ; 
as hypophosphor ous, phosphorous and j)hosphoric acids; hypochlorous, chlorous, 
hypochloric, chloric, and perchloric acids ; nitrous, hyponitric, and nitric acids, &c. 

The nomenclature of salts is derived from that of the acid they contain ; 
if the name of the acid terminate in ic, that of the salt is made to end in ate ; 
if in ous, that of the saline compounds ends in ite. Thus, sulphuric acid forms 
sulphates of the various bases; sulphurous acid, sulphites; hyposulphurous 
acid, hyposulphites ; hyposulphuric acid, hypo sulphates, &c. The rule here is 
very simple and obvious. 

1 Formerly the termination uret was like-wise frequently used. 



172 GENERAL PRINCIPLES OF 

The want of uniformity in the application of the systematic nomenclature 
is chiefly felt in the class of oxides not possessing acid characters, and in 
that of some analogous compounds. The old rule was to apply the word 
protoxide to the oxide containing least oxygen, to call the next in order bin- 
oxide, the third iritoxide, or teroxide ; &c. But latterly this rule has been 
broken through, and the term protoxide given to that oxide q£ a series in 
which the basic characters are most strongly marked. Any compound con- 
taining a smaller proportion of oxygen than this is called a suboxide. An 
example is to be found in the two oxides of copper ; that which was once 
called binoxide is now protoxide, being the most basic of the two, while the 
former protoxide is degraded into suboxide. 

The Latin prefix per, or rarely hyper, is sometimes used to indicate the 
highest oxide of a series destitute of acidity, as peroxide of iron, chromium, 
manganese, lead, &c. Other Latin prefixes, as sesqui, bi or bin, and quad, 
applied to the name of binary compounds or salts, have reference to the con- 
stitution of these latter expressed in chemical equivalents. 1 Thus, an oxide 
in which the proportion of oxygen and metal are in equivalents, as 1-5 to 1, or 
3 to 2, is often called a sesquioxide ; if in the proportion of 2 to 1, a binoxide, 
&c. The same terms are applied to salts ; thus we have neutral sulphate of 
potassa, sesquisutphate of potassa, and bisulphate of potassa; the first con- 
taining 1 equivalent of acid to 1 of base, the second 1*5 of acid to 1 of base, 
and the third 2 equivalents of acid. to 1 equivalent of base. In like manner 
we have neutral oxalate, binoxalate, and quadroxalate of potassa, the latter 
having 4 eq. of acid to 1 eq. of base. Many other cases might be cited. 

The student will soon discover that the rules of nomenclature are often 
loosely applied, as when a Latin numeral prefix is substituted for one of 
Greek origin. We speak of tcrsulphide instead of tritosulphide of antimony. 
These and other small irregularities are not found in practice to cause seri- 
ous confusion. 

THE LAWS OF COMBINATION BY WEIGHT. 

The great general laws which regulate all chemical combinations admit of 
being laid down in a manner at once simple and concise. They are four in 
number, and to the following effect : — 

1. All chemical compounds are definite in their nature, the ratio of the 
elements being constant. 

2. Vv T hen any body is capable of uniting with a second in several pro- 
portions, these proportions bear a simple relation to each other. 

3. If a body, A, unite with other bodies, B, C, D, the quantities of 
B, C, D, which unite with A, represent the relations in which they unite 
among themselves, in the event of union taking place. 

4. The combining quantity of a compound is the sum of the combining 
quantities of its components. 

(1.) Constancy of Composition. — That the same chemical compound invari- 
ably contains the same elements united in unvarying proportions, is a propo- 
sition almost axiomatic; it is involved in the very idea of identity itself. 
The converse, however, is very far from being true ; the same elements com- 
bining in the same proportions do not of necessity generate the same 
substance. 

Organic chemistry furnishes numerous instances of this very remarkable 
fact, in which the greatest diversity of properties is associated with identity 
of chemical composition. These cases seem to be nearly confined to organic 

1 See a few pages forward. 



CHEMICAL PHILOSOPHY. 173 

chemistry ; only a few well-established and undoubted examples being known 
in the organic or mineral division of the science. 

(2.) Multiple Proportions. — Illustrations of this simple and beautiful law 
abound on every side ; let the reader take for example the compounds of 
nitrogen and oxygen, five in number, containing the proportions of the two 
elements so described that the quantity of one of them shall remain con- 
stant: — 

Nitrogen. Oxygen. 

Protoxide 14 8 

Binoxide 14 16 

Nitrous acid 14 24 

Hyponitric acid 14 32 

Nitric acid 14 40 

It will be seen at a glance, that while the nitrogen remains the same, the 
quantities of oxygen increase by multiples of 8, or the number representing 
the quantity of that substance in the first compound; thus 8, 8x2, 8x3, 
8x4, and 8x5, give respectively the oxygen in the protoxide, the binoxide, 
nitrous acid, hyponitric acid, and lastly, nitric acid. Again, carbonic acid 
contains exactly twice as much oxygen in proportion to the other constituent 
as carbonic oxide ; the binoxide of hydrogen is twice as rich in oxygen as 
water: the corresponding sulphides exhibit the same phenomena, while the 
metallic compounds offer one continued series of illustrations of the law, 
although the ratio is not always so simple as that of 1 to 2. 

It often happens that one or more members of a series are yet deficient: 
the oxides of chlorine afford an example 

Chlorine. Oxygen. 

Rypochlorous acid 35-5 8 

Chlorous acid 35-5 24 

Hypochloric acid 35-5 32 

Chloric acid 35-5 40 

Perchloric acid 35-5 56 

Here the quantities of oxygen progress in the following order! — 8, 8x3, 
8x4, 8x5, 8x7; a gap is manifest between the first and second substances; 
this remains to be filled up by future researches. The existence of a simple 
relation among the numbers in the second column is however not the less 
evident. Even when difficulties seem to occur in applying this principle, 
they are only apparent, and vanish when closely examined. In the highly 
complex sulphur series, given at p. 132, the numbers placed in each column 
are multiples of the lowest amongst them ; and, by making the assumption, 
which is not at all extravagant, that certain of the last-named bodies are in- 
termediate combinations, we may arrange the four direct compounds in such 
a manner that the sulphur shall remain a constant quantity. 

Sulphur. Oxygen. 

Hyposulphurous acid 32 16 

Sulphurous acid 32 32 

Hyp osulphuric acid 32 ...... 40 

Sulphuric acid 32 48 

Compound bodies of all kinds are also subject to the law of multiples 
when they unite among themselves, or with elementary substances. There 
are two sulphates of potassa and soda: the second contains twice as much 
acid in relation to the alkaline base as the first. There are three oxalates 
of potassa, namely, the simple oxalate, the binoxalate, and the quadroxalate • 
15* 



174 GENERAL PRINCIPLES OF 

the second has equally twice as much acid as the first; and the third twice 
as much as the second. Many other cases might be cited, but the student, 
once in possession of the principle, will easily notice them as he proceeds. 

(3.) Law of Equivalents. — It is highly important that the subject now to 
be discussed should be completely understood. 

Let a substance be chosen whose range of affinity and powers of combi- 
nation are very great, and whose compounds are susceptible of rigid and 
exact analysis ; such a body is found in oxygen, which is known to unite 
with all the elementary substances, with the single exception of fluorine. 
Now, let a series of exact experiments be made to determine the proportions 
in which the different elements combine with one and the same constant 
quantity of oxygen, which, for reasons hereafter to be explained, may be 
assumed to be 8 parts by weight ; and let these numbers be arranged in a 
column opposite the names of the substances. The result is a table or list 
like the following, but of course much more extensive when complete. 

Oxygen 8 

Hydrogen 1 

Nitrogen 14. 

Carbon 6 

Sulphur 16 

Phosphorus 32 

Chlorine 35'5 

Iodine 127 

Potassium 39 

Iron 28 

Copper 31-7 

Lead 103-7 

Silver 108 

&c. &c. 

Now the law in question is to this effect : — If such numbers represent 
the proportions in which the different elements combine with the arbitrarily- 
fixed quantity of the starting substance, the oxygen, they also represent the 
proportions in which they unite among themselves, or at any rate bear some ex- 
ceedingly simple ratio to these proportions. 

Thus, hydrogen and chlorine combine invariably in the proportions 1 and 
35-5; hydrogen and sulphur, 1 to 16; chlorine and silver, 35-5 to 108; 
iodine and potassium, 127 parts of the former to 39 of the latter, &c. This 
rule is never departed from in any one instance. 

The term equivalent is applied to these numbers for a reason which will 
now be perfectly intelligible ; they represent quantities capable of exactly 
replacing each other in combination : 1 part of hydrogen goes as far in com- 
bining with or saturating a certain amount of oxygen as 28 parts of iron, 39 
of potassium, or 108 of silver; for the same reasons, the numbers are said 
to represent combining quantities, or proportionals. 

Nothing is more common than to speak of so many equivalents of this or 
that substance being united to one or more equivalents of a second ; by this 
expression, quantities are meant just so many times greater than these rela- 
tive numbers. Thus, sulphuric acid is said to contain 1 equivalent of sul- 
phur and 3 equivalents of oxygen ; that is, a quantity of the latter repre- 
sented by three times the combining number of oxyjren ; phosphoric acid is 
made up of 1 equivalent of phosphorus and 5 of oxygen; the red oxide of 
iron contains, as will be seen hereafter, 3 equivalents of oxygen to every 2 
equivalents of metal, &c. It is an expression which will henceforward be 



CHEMICAL PHILOSOPHY. 1? 5 

freely and constantly employed ; it is hoped, therefore, that it will be under- 
stood. 

The nature of the law will easily show that the choice of the body destined 
to serve for a point of departure is perfectly arbitrary, and regulated by con- 
siderations of convenience alone. 

A body might be chosen which refuses to unite with a considerable num- 
ber of the elements, and yet the equivalents of the latter would admit of 
being determined by indirect means, in virtue of the very peculiar law under 
discussion. Oxygen does not unite with fluorine, yet the equivalent of the 
latter can be found by obsei-ving the quantity which combines with the equi- 
valent quantity of hydrogen or calcium, already known. We may rest as- 
sured that if an oxide of fluorine be ever discovered, its elements will be 
associated in the ratio of 8. to 19, or in numbers which are either multiples 
or submultiples of these. 

The number assigned to the starting-substance is also equally arbitrary ; 
if, in the table given, oxygen instead of 8 were made 10, or 100, or even a 
fractional number, it is quite obvious that although the other numbers would 
all be different, the ratio, or proportion among the whole, would remain un- 
changed, and the law would still be maintained in all its integrity. 

There are in fact two such tables in use among chemists ; one in which 
oxygen is made = 8, and a second in which it is made = 100 ; the former 
is generally used in this country and England, and the latter still to a 
certain extent on the Continent. The only reason for giving, as in the pre- 
sent volume, a preference to the first is, that the numbers are smaller and 
more easily remembered. 

The number 8 has been chosen in this table to represent oxygen, from an 
opinion long held by the late Dr. Prout, and recently to appearance substan- 
tiated in some remarkable instances by very elaborate investigation, that the 
equivalents of all bodies are multiplies of that of hydrogen ; and, conse- 
quently, by making the latter unity, the numbers would be all integers. The 
question must be considered as altogether unsettled. A great obstacle to 
such a view is presented by the case of chlorine, which certainly seems to be 
a fractional number ; and one single well-established exception will be fatal 
to the hypothesis. 

As all experimental investigations are attended with a certain amount of 
error, the results contained in the following table must be looked upon 
merely as good approximations to the truth. For the same reason, small 
differences are often observed in the determination of the equivalents of the 
same bodies by different experimentei's. 



176 



GENERAL PRINCIPLES OP 



TABLE OF ELEMENTARY SUBSTANCES, "WITH THEIR EQUIVALENTS. 





0xy. = 8. 


Oxy.=100 


Aluminium . . 


.. 13-7 


171-25 


Antimony... 


..129 


1612-5 




.. 75 

.. 68-5 


937-5 


Barium 


856-25 


Beryllium... 


.. 6-9 


86-25 


Bismuth 


..213 


2662-5 


Boron 


.. 10-9 


136-25 


Bromine .... 


.. 80 


1000 


Cadmium ... 


.. 56 


700 


Calcium 


.. 20 


250 


Carbon 


.. 6 


75 


Cerium 


.. 47(?) 


587-5 


Chlorine 


.. 35-5 


443-75 


Chromium.. 


.. 26-7 


333-75 


Cobalt 


.. 29-5 


368-75 


Copper 


.. 31-7 


396-25 


Bidymium .. 


.. 50(?) 


625 


Erbium 






Fluorine 


.. 19 


237.5 


Gold! 


..197 


2462-5 


Hydrogen... 


.. 1 


12-5 


Iodine 


..127 


1587-5 


Iridium 


.. 99 


1237-5 


Iron 


.. 28 


350 


Lanthanum 


.. 47(?) 


587-5 


Lead 


..103-7 


1296-25 


Lithium 


.. 6-5 


81-25 


Magnesium 


.. 12 


150 


Manganese. 


.. 27-6 


345 


Mercury .... 


..100 


1250 


Molybdenum 


.. 46 


575 



Oxy. = 8. 

Nickel 29-6 

Niobium 

Nitrogen 14 

Norium 

Osmium 99-6 

Oxygen 8 

Palladium 53-3 

Pelopium 
Phosphorus.... 32 

Platinum 98-7 

Potassium 39 

Rhodium 52-2 

Ruthenium.... 52-2 

Selenium 39-5 

Silicium 21-3 

Silver 108 

Sodium 23 

Strontium 43-8 

Sulphur 16 

Tantalum 184 

Tellurium 64-2 

Terbium 

Thorium 59-6 

Tin 58 

Titanium 25 

Tungsten 92 

Uranium 60 

Vanadium 68-6 

Yttrium 

Zinc 32-6 

Zirconium 33-6 



Oxy.=100. 
370 

175 

1245 

100 
666-25 

400 

1233-75 
487-5 
652-5 
652-5 
493-75 
266-25 

1350 
287-5 
547-5 
200 

2300 
802-5 

745 

725 
312-5 
1150 
750 
857-5 

407-5 
420 



(4.) Combining Numbers of Compounds. — The law states that the equivalent 
or combining number of a compound is always the sum of the equivalents 
of its components. This is also a great fundamental truth, which it is neces- 
sary to place in a clear and conspicuous light. It is a separate and inde- 
pendent law, established by direct experimental evidence, and not deducible 
from either of the preceding. 

The method of investigation by which the equivalent of a simple body is 
determined, has been already explained ; that employed in the case of a com- 
pound is in nowise different. The example of the acids and alkalis may be 
taken as the most explicit, and at the same time most important. An acid 
and a base, combined in certain definite proportions, neutralize, or mask each 
other's properties completely, and the result is a salt ; these proportions are 
called the equivalents of the bodies, and they are very variable. Some acids 
have very high capacities of saturation, of others a much larger quantity 
must be employed to neutralize the same amount of base : the bases them- 
selves present also similar phenomena. Thus, to saturate 47 parts of potassa, 
or 116 parts of oxide of silver, there are required 



CHEMICAL PHILOSOPHY. 177 

40 parts sulphuric acid, 
54 " nitric acid, 
75-5 " chloric acid, 
167 " iodic acid, 
51 " acetic acid. 

Numbers very different, hut representing quantities which replace each 
other in combination. Now, if a quantity of some base, such as potassa, be 
taken, which is represented by the sum of the equivalents of potassium and 
oxygen, then the quantity of any acid requisite for its neutralization, as de- 
termined by direct experiment, will always be found equal to the sum of the 
equivalents of the different components of the acid itself. 

39= equivalent of potassium. 
8= " oxygen. 

47 = assumed equivalent of potassa. 

47 parts of potassa are found to be exactly neutralized by 40 parts of real 
sulphuric acid, or by 54 parts of real nitric acid. These quantities are 
evidently made up by adding together the equivalents of their constituents : — ■ 

1 equivalent of sulphur = 16 1 equivalent of nitrogen = 14 

3 " oxygen = 24 5 " oxygen = 40 

1 " sulphuric acid = 40 1 " nitric acid = 54 

And the same is true if any acid be taken, and the quantities of different 
bases required for its neutralization determined ; the combining number 
of the compound will always be found to be the sum of the combining num- 
bers of its components, however complex the substance may be. Even 
among such bodies as the vegeto-alkalis of organic chemistry, the same uni- 
versal rule holds good. When salts combine, which is a thing of very com- 
mon occurrence, as will hereafter be seen, it is always in the ratio of the 
equivalent numbers. Apart from hypothetical consideration, no cL priori 
reason can be shown why such should be the case ; it is, as before remarked, 
an independent law, established like the rest, by experiment. 



A curious observation was very early made to this effect : — If two neutra 
salts which decompose each other when mixed, be brought in contact, the 
new compounds resulting from their mutual decomposition will also be neutral. 
For example, when solution of nitrate baryta and sulphate of potassa are 
mingled, they both suffer decomposition, sulphate of baryta and nitrate of 
notassa being simultaneously formed, both of which are perfectly neutral. 
The reason of this will be at once evident ; interchange of elements can 
only take place by the displacement of equivalent quantities of matter on 
either side. For every 54 parts of nitric acid set free by the decomposition 
of the barytic salt, 47 parts of potassa are abandoned by the 40 parts of 
sulphuric acid with which they were previously in combination, now trans- 
ferred to the baryta. But 54 and 47 are the representatives of combining 
quantities ; hence the new compound must be neutra. 

COMBINATION BY VOLUME. 

Many years ago, M. Gay-Lussac made the very important and interesting 
discovery that when gases combine chemically, union invariably takes place 
either between equal volumes, or between volumes which bear a simple rela- 
tion to each other. This is not only true of elementary gases, but of com 



778 GENERAL PRINCIPLES OP 

pound bodies of this description, as it is invariably observed that the con- 
traction of bulk -which so frequently follows combination itself also bears a 
simple relation to the volumes of the combining gases. The consequence 
of this is, that compound gases and the vapours of complex volatile liquids 
(which are truly gases to all intents and purposes) follow the same law as 
elementary bodies, when they unite with these latter or combine among them- 
selves. 

The ultimate reason of the law in question is to be found in the very 
remarkable relation established by the hand of Nature between the specific 
gravity of a body in the gaseous state and its chemical equivalent ; — a rela- 
tion of such a kind that quantities by weight of the various gases expressed 
by their equivalents, or in other words, quantities by weight which combine, 
occupy under similar circumstances of pressure and temperature either equal 
volumes, or volumes bearing a similar proportion to each other. In the 
example cited below, equivalent weights of hydrogen, chlorine, and iodine- 
vapour, occupy equal volumes, while the equivalent of oxygen occupies 
exactly half that measure. 

Cubic inches. 
8-0 grains of oxygen occupy at 60° (15°-5C) and 30 inches barom. 23-3 

1-0 grain of hydrogen 46-7 

35-5 grains of chlorine 46-2 

127-0 grains of iodine-vapour (would measure) 46-7 

If both the specific gravity and the chemical equivalent of a gas be known, 
its equivalent or combining volume can be easily determined, since it will be 
represented by the number of times the weight of an unit of volume (the 
specific gravity) is contained in the weight of one chemical equivalent of the 
substance. In other words, the equivalent volume is found by dividing the 
chemical equivalent by the specific gravity. The following table exhibits 
the relations of specific gravity, equivalent weight, and equivalent volume 
of the principal elementary substances. 

Sp. gravity. Equiv. weight. Equiv. volume. 

Hydrogen 0-0693 1-0 14-43 or 1 

Nitrogen 0-972 14-0 14-37 " 1 

Chlorine 2-470 35-5 14-33 " 1 

Bromine-vopour 5-395 80-0 14-82 " 1 

Iodine-vapour 8-716 127-0 14-57 " 1 

Carbon- vapour 1 0-418 6-0 14-34 « 1 

Mercury-vapour 7-000 100-0 14-29 « 1 

Oxygen 1-106 8-0 7-23 " £ 

Phosphorus-vapour 4-350 ... 32-0 7-35 " | 

Arsenic-vapour 10-420 75-0 7-19 " | 

Sulphur-vapour 6-654 16 2-40 " J 

Thus it appears that hydrogen, nitrogen, chlorine, bromine, iodine, carbon, 
and mercury, in the gaseous state, have the same equivalent volume ; oxygen, 
phosphorus, and arsenic, one-half of this; and sulphur one-sixth. The 
plight discrepancies in the numbers in the third column result chiefly from 
errors in the determination of the specific gravities. 

Compound bodies exhibit exactly similar results : — 



See farther on. 



CHEMICAL PHILOSOPHY. 179 

Sp. gravity. Equiv. weight. Equiv. volume. 

Water-vapour 0-625 .... 9-0 .... 14-40 or 1 

Protoxide of nitrogen 1-525 .... 22-0 .... 14-43 " 1 

Sulphuretted hvdrogen 1-171 .... 17-0 .... 14-51 " 1 

Sulphurous aciu 2-210 .... 32-0 .... 14-52 » 1 

Carbonic oxide 0-973 .... 14-0 ... 14-39 « 1 

Carbonic acid 1-524 .... 22-0 .... 14-43"! 

Light carbonetted hydrogen 0-559 .... 8-0 .... 14-31 " 1 

defiant gas 0-981 .... 14-0 .... 14-27 » j 

Binoxide of nitrogen 1-039 .... 30-0 .... 28-87 " 2 

Hydrochloric acid 1-269 .... 36-5 .... 28-70 " 2 

Phosphoretted hydrogen 1-240 .... 35-0 .... 28-22 " 2 

Ammonia 0-589 .... 17-0 .... 28-86 « 2 

Ether-vapour 2-586 .... 37-0 .... 14-31 " 1 

Acetone-vapour 2-022 .... 290 .... 14-34 " 1 

Benzol-vapour 2-738 .... 78-0 .... 28-49 « 2 

Alcohol-vapour, 1-613 .... 46-0 .... 28-52 « 2 

In the preceding tables the ordinary standard of specific gravity for gases, 
atmospheric air, has been taken. It is, however, a matter of perfect indif- 
ference what substance be chosen for this purpose ; the numbers represent- 
ing the combining volumes will change with the divisor, but the proportions 
they bear to each other will remain unaltered. And the same remark 
applies to the equivalent weights ; either of the scales in use may be taken, 
provided that it be adhered to throughout. 

The law of volumes often serves in practice to check and corroborate the 
results of experimental investigation, and is often of great service in this 
respect. 

There is an expression sometimes made use of in chemical writings which 
it is necessary to explain, name]}', the meaning of the words hypothetical den- 
sity of vapour, applied to a substance which has never been volatilized, such 
as carbon, whose real specific gravity in that state must of course be un- 
known; it is easy to understand the origin of this term. Carbonic acid con- 
tains a volume of oxygen equal to its own ; consequently, if the specific 
gravity of the latter be subtracted from that of the former gas, the residue 
will express the proportion borne by the weight of the carbon, certainly 
then in a vaporous state, to that of the two gases. 

The specific gravity of carbonic acidis 1-5240 

That of oxygen is 1-1057 



0-4183 



On the supposition that carbonic acid contains equal volumes of oxygen 
and this vapour of carbon, condensed to one-half, the latter will have the 
specific gravity represented by 0-4183 and the combining volume given in the 
table. But this is merely a supposition, a guess ; no proof can be given 
that carbonic acid gas is so constituted. All that can be safely said is con- 
tained in the prediction, that, should the specific gravity of the vapour of 
carbon ever be determined, it will be found to coincide with this number, or 
to bear some simple and obvious relation to it. 

For many years past, attempts have been made to extend to solids and 
liquids the results of Gay-Lussac's discovery of the law of gaseous combi- 
nation by volume, the combining or equivalent volumes of the bodies in 
question being determined by the method pursued in the case of gases, 
namely, by dividing the chemical equivalent by the specific gravity. The 



180 



GENERAL PRINCIPLES OF 



numbers obtained in this manner representing the combining volumes of the 
Various solid and liquid elementary substances, present far more cases of 
discrepancy than of agreement. The latter are, however, sufficiently nu- 
merous to excite great interest in the investigation. Some of the results 
pointed out are exceedingly curious as far as they go, but are not as jet 
sufficient to justify any general conclusion. The inquiry is beset "with many 
great difficulties, chiefly arising from the unequal expansion of solids and 
liquids by heat, and the great differences of physical state, and consequently 
of specific gravity, often presented by the former. 

Such is a brief account of the great laws by which chemical combinations, 
of every kind, are governed and regulated ; and it cannot be too often re- 
peated, that the discovery of these beautiful laws has been the result of 
pure experimental inquiry. They have been established on this firm and 
stable foundation by the joint labours of very many illustrious men; they 
are the expression of fact, and are totally independent of all hypotheses or 
theories whatsoever. 

CHEMICAL NOTATION; SYMBOLS. 

For convenience in communicating ideas respecting the composition, and 
supposed constitution, of chemical compounds, and explaining in a clear and 
simple manner, the results of changes they may happen to undergo, re- 
course is had to a kind of written symbolical language, the principle of 
which must now be explained. To represent compounds by symbols is no 
novelty, as the works of the Alchemists will show, but these have been mere 
arbitrary marks or characters invented for the sake of brevity, or sometimes 
perhaps for that of obscurity. 

The plan about to be described is due to Berzelius ; it has been adopted, 
with slight modifications, wherever chemistry is pursued. 

Every elementary substance is designated by the first letter of its Latin 
name, in capital, or by the first letter conjoined with a second small one, the 
most characteristic in the word, as the names of many bodies begin alike. 
The single letter is usually confined to the earliest discovered, or most im- 
portant element. Farther, by a most ingenious idea, the symbol is made to 
represent not the substance in the abstract, but one equivalent of that sub- 
stance. 

Table of Symbols of the Elementary Bodies. 



Aluminium Al 

Antimony (Stibium) Sb 

Arsenic As 

Barium Ba 

Beryllium Be 

Bismuth Bi 

Boron , Bo 

Bromine Br 

Cadmium Cd 

Calcium Ca 

Carbon C 

Cerium Ce 

Chlorine CI 

Chromium Cr 

Cobalt Co 

Copper (Cuprum) Cu 

Didymium Dy 

Ei'bium Er 

Fluorine F 



Gold (Aurum) Au 

Hydrogen H 

Iodine I 

Iridium Ir 

Iron (Ferrum) Fe 

Lantanum Ln 

Lead (Plumbum) Pb 

Lithium L 

Magnesium Mg 

Manganese Mti 

Mercury ( Hydrargyrum ) . . . . 11 g 

Molybdenum Mo 

Nickel Ni 

Niobium Nb 

Nitrogen N 

Norium No 

Osmium Os 

Oxygen O 

Palladium Pd 



CHEMICAL PHILOSOPHY. 



181 



Pelopium Pe 

Phosphorus P 

Platinum Pt 

Potassium (Kalium) K 

Rhodium R 

Ruthenium Ru 

Selenium Se 

Silicium Si 

Silver (Argentum) Ag 

Sodium (Natrium) Na 

Strontium Sr 

Sulphur S 



Tantalum Ta 

Tellurium Te 

Terbium Tb 

Thorium Th 

Tin (Stannum) Sn 

Titanium Ti 

Tungsten (Wolframium) W 

Vanadium V 

Uranium U 

Yttrium Y 

Zinc Zn 

Zirconium Zr 



Combination between bodies in the ratio of the equivalents is expressed 
by mere juxtaposition of the symbols, or sometimes by interposing the sign 
of addition. Por example : — 

Water HO, orH + O 

Hydrochloric acid HC1, or H -f CI 
Protoxide of iron PeO, or Pe -f- 

"When more than one equivalent is intended, a suitable number is added, 
sometimes being placed before the symbol, like a co-efficient in algebra, 
sometimes appended after the manner of an exponent, but more commonly 
placed a little below on the right. 

Rinoxide of hydrogen H + 20, or HO 2 , or HO a 

Sulphuric acid S + 30, or SO 3 , or S0 3 

Hyposulphuric acid.. 2S + 50, or S 2 5 or S 2 5 

Combination between bodies themselves compound is indicated by the sign 
of addition, or by a comma. When both are used in the same formula, the 
latter may be very conveniently applied, as Professor Graham has suggested, 
to indicate the closest and most intimate union. A number standing before 
symbols, inclosed within a bracket, signifies that the whole of the latter are 
to be multiplied by that number. Occasionally the bracket is omitted, when 
the number affects all the symbols between itself and the next sign. A few 
examples will serve to illustrate these several points. 

Sulphate of soda NaO + S0 3 , or NaO , S0 3 
Nitrate of potassa KO + N0 5 , or KO , NO a 

The base being always placed first. 

Double sulphate of copper and potassa CuO , SOg-j-KO , S0 3 

The same in a crystallized state CuO , S0 3 -f-KO , S0 3 -f 6H0 

Common crystallized alum, or double sulphate of alumina and potassa, is 
thus written : — 



In expressing organic compounds, where three or more elements exist, the 
same plan is used. 

Sugar C 12 H n O n 

Alcohol C 4 H 6 2 

Acetic acid HO , CJI s 3 

Morphine 
Acetate o1 
Acetate of soda NaO 



16 



; > C 4 H 3°a 
C 4 H 3 3 



182 GENERAL PRINCIPLES OF 

By such a system, the eye is enabled to embrace the whole at a glance, 
and gain a distinct idea of the composition of the body, and its relations to 
others similarly described. 



Some authors are in the habit of making use of contractions, -which, how- 
ever, are by no means generally adopted. Thus, two equivalents of a sub- 
stance are indicated by the symbol with a short line drawn through or below 
it ; an equivalent of oxygen is signified by a dot, and one of sulphur by a 
comma. These alterations are sometimes convenient for abbreviating a long 
formula, but easily liable to mistakes. Thus, 

Sesquioxide of iron FeO 3 , or F eO 3 , or Fe, instead of Fe 2 3 

Bisulphide of carbon C, instead of CS 2 

Crystallized alum as before AlS 3 -j-KS-j-24H. 

THE ATOMIC THEORY. 

That no attempt should have been made to explain the reason of the very 
remarkable manner in which combination occurs in the production of che- 
mical compounds, and to point out the nature of the relations between the 
different modifications of matter which fix and determine these peculiar and 
definite changes, would have been unlikely, and in contradiction with the 
speculative tendency of the human mind. Such an attempt, and a very inge- 
nious and successful one it is, has been made, namely, the atomic hypothesis 
of Dr. Dalton. 

From very ancient times, the question of the constitution of matter with, 
respect to divisibility has been debated, some adopting the opinion that this 
divisibility is infinite, and others, that when the particles become reduced to 
a certain degree of tenuity, far indeed beyond any state that can be reached 
by mechanical means, they cease to be farther diminished in magnitude ; 
they become, in short, atoms. 1 Now, however the imagination may succeed 
in figuring to itself the condition of matter on either view, it is hardly neces- 
sary to mention that we have absolutely no means at our disposal for deciding 
such a question, which remains at the present day in the same state as when 
it first engaged the attention of the Greek philosophers, or perhaps that of 
the sages of Egypt and Hindostan long before them. 

Dr. Dalton's hypothesis sets out by assuming the existence of such atoms 
or indivisible particles, and states, that compounds are formed by the union 
of atoms of different bodies, one to one, one to two, &c. The compound atom 
joins itself in the same manner to a compound atom of another kind, and a 
combination of the second order results. Let it be granted, farther, that the 
relative weights of the atoms are in the proportions of the equivalent numbers, 
and the hypothesis becomes capable of rendering consistent and satisfactory 
reasons for all the consequences of those beautiful laws of combination lately 
discussed. 

Chemical compounds must always be definite ; they must always contain 
the same number of atoms, of the same kind, arranged in a similar manner. 
The same kind and number of atoms need not, however, of necessity produce 
the same substance, for they may be differently arranged ; and much depends 
upon this circumstance. 

Again, the law of multiple proportions is perfectly well explained ; an atom 

1 "Aro/^ojj that which cannot be cut. 



CHEMICAL PHILOSOPHY. 183 

of nitrogen unites •with one of oxygen to form laughing gas ; with two, to 
form binoxide of nitrogen ; with three, to produce nitrous acid ; with four, 
hyponitric acid ; and -with five, nitric acid, — perhaps something after the 
manner represented in fig. 124, in which the circle with a cross represents 
the atom of nitrogen, and the plain circle that of oxygen. 

Fig. 124. 
Protoxide. Biooxioe. *%- "*J«j«* 



00 OK) 




Two atoms of one substance may unite themselves with three or even with 
seven of another, as in the case of one of the acids of manganese ; but such 
combinations are rare. 

The mode in which bodies replace, or may be substituted for, each other, 
is also perfectly intelligible, as a little consideration will show. 

Finally, the law which fixes the equivalent of a compound at the sum of 
the equivalents of the components, receives an equally satisfactory expla- 
nation. 

The difficulties in the general application of the atomic hypothesis are 
chiefly felt in attempting to establish some wide and universal relation be- 
tween combining number and combining volume, among gases and vapours, 
and in the case of the highly complex products of organic chemistry. These 
obstacles have grown up in comparatively recent times. On the other hand, 
the remarkable observations of the specific capacities for heat of equivalent 
quantities of the solid elementary substances, might be urged in favour of 
this or some similar molecular hypothesis. But even here serious discrep- 
ancies exist ; we may not take liberties with equivalent numbers determined 
by exact chemical research, and, in addition, a simple relation is generally 
found to be wanting between the capacity for heat of the compound and that 
of its elements. 

The theory in question has rendered great service to chemical science ; it 
has excited a vast amount of inquiry and investigation, which have contribu- 
ted very largely to define and fix the laws of combination themselves. In 
more recent days it is not impossible, that, without some such hypothetical 
guide, the exquisitely beautiful relations which Mitscherlich and others have 
shown to exist between crystalline form and chemical composition, might 
never have been brought to light, or, at any rate, their discovery might 
have been greatly delayed. At the same time, it is indispensable to draw 
the broadest possible line of distinction between this, which is at the best 
but a graceful, ingenious, and, in its place, useful hypothesis, and those 
great general laws of chemical action which are the pure and unmixed result 
of inductive research. 1 



Chemical Affinity. 

The term chemical affinity, or chemical attraction, has been invented to 
describe that particular power or force, in virtue of which, union,- often of a 
very intimate and permanent nature, takes place between two or more 

1 The expression atomic weight is very often substituted for that of equivalent weight and 
is, in fact, iu almost every case to be understood as such: it is, perhaps, Letter avoided. 



184 GENERAL PRINCIPLES OF 

bodies, in such a way as to give rise to a new substance, having, for the most 
part, properties completely in discordance with those of its components. 

The attraction thus exerted between different kinds of matter is to be dis- 
tinguished from other modifications of attractive force which are exerted 
indiscriminately between all descriptions of substances, sometimes at enor- 
mous distances, and sometimes at intervals quite inappreciable. Examples 
of the latter are to be seen in cases of what is called cohesion, when the par- 
ticles of solid bodies are immovably bound together into a mass. Then 
there are other effects of, if possible, a still more obscure kind ; such as the 
various actions of surface, the adhesion of certain liquids to glass, the re- 
pulsion of others, the ascent of water in narrow tubes, and a multitude of 
curious phenomena which are described in works on Natural Philosophy, 
under the head of molecular actions. From all these, true chemical attraction 
may be at once distinguished by the deep and complete change of characters 
which follows its exertion; we might define affinity to be a force by which 
new substances are generated. 

It seems to be a general law that bodies most opposed to each other in 
chemical properties evince the greatest tendency to enter into combination, 
and, conversely, bodies between which strong analogies and resemblances 
can be traced, manifest a much smaller amount of mutual attraction. For 
example, hydrogen and the metals tend very strongly indeed to combine with 
oxygen, chlorine, and iodine ; the attraction between the different members 
of these two groups is incomparably more feeble. Sulphur and phosphorus 
stand, as it were, mid-way; they combine with substances of one and the 
other class, their properties separating them sufficiently from both. Acids 
are drawn towards alkalis, and alkalis towards acids, while union among 
themselves rarely, if ever, takes place. 

Nevertheless, chemical combination graduates so imperceptibly into mere 
mechanical mixture, that it is often impossible to mark the limit. Solution 
is the result of a weak kind of affinity existing between the substance dis- 
solved and the solvent ; an affinity so feeble as completely to lose one of its 
most prominent features when in a more exalted condition, namely, power of 
causing elevation of temperature ; for in the act of mere solution the tem- 
perature falls, the heat of combination being lost and overpowered by the 
effects of change of state. 

The force of chemical attraction thus varies greatly with the nature of 
the substances between which it is exerted ; it is influenced, moreover, to a 
very large extent by external or adventitious circumstances. An idea for- 
merly prevailed that the relations of affinity were fixed and constant between 
the same substances, and great pains were taken in the preparation of tables 
exhibiting what was called the precedence of affinities. The order pointed 
out in these lists is now acknowledged to represent the order of precedence 
for the circumstances under which the experiments were made, but nothing 
more ; so soon as these circumstances become changed, the order is disturbed. 
The ultimate effect, indeed, is not the result of the exercise of one single 
force, but rather the joint effect of a number, so complicated and so variable 
in intensity, that it is but seldom possible to predict the consequences of any 
yet untried experiment. The following may serve as examples of the tables 
alluded to ; the first illustrates the relative affinities of a number of bases 
for sulphnric acid, each decomposing the combination of the acid with the 
base below it; thus, magnesia decomposes sulphate of ammonia; lime dis- 
places the acid from sulphate of magnesia, &c. The salts are supposed to 
be dissolved in water. The second table exhibits the order of affinit}' for 
oxygen of several metals, mercury reducing a solution of silver, copper one 
of mercury, &c. 



CHEMICAL PHILOSOPHY. 185 



Sulphuric acid. 
Baryta, Lime, 

Strontia, Magnesia, 

.Potassa, Ammonia. 

Soda, 



Oxygen. 
Zinc, Mercury, 

Lead, Silver. 

Copper, 



It •will be proper to examine shortly some of these extraneous causes to 
•which allusion has been made, which modify to so great an extent the direct 
and original effects of the specific attractive force. 

Alteration of temperature may be reckoned among these. When metallic 
mercury is heated nearly to its boiling point, and in that state exposed for a 
lengthened period to the air, it absorbs oxygen, and becomes converted into 
a dark red crystalline powder. This very same substance, when raised to 
a still higher temperature, spontaneously separates into metallic mercury 
and oxygen gas. It may be said, and probably with truth, that the latter 
change is greatly aided by the tendency of the metal to assume the vaporous 
state ; but, precisely the same fact is observed with another metal, palladium, 
which is not volatile at all, but which oxidates superficially at a red-heat, 
and again becomes reduced when the temperature rises to whiteness. 

Insolubility and the power of vaporization are perhaps, beyond all other 
disturbing causes, the most potent ; they interfere in almost every reaction 
which takes place, and very frequently turn the scale when the opposed forces 
do not greatly differ in energy. It is easy to give examples. When a solu- 
tion of lime in hydrochloric acid is mixed with a solution of carbonate of 
ammonia, double interchange ensues, carbonate of lime and hydrochlorate 
of ammonia being generated. Here the action can be shown to be in a great 
measure determined by the insolubility of the carbonate of lime. Again, 
dry carbonate of lime, powdered and mixed with hydrochlorate of ammonia, 
and the whole heated in a retort, gives a sublimate of carbonate of ammonia, 
while chloride of calcium remains behind. In this instance, it is no doubt 
the great volatility of the ammoniacal salt which chiefly determines the kind 
of decomposition. 

When iron-filings are heated to redness in a porcelain tube, and vapour of 
water passed over them, the water undergoes decomposition with the utmost 
facility, hydrogen is rapidly disengaged, and the iron converted into oxide. 
On the other hand, oxide of iron heated in a tube through which a stream 
of dry hydrogen is passed, suffers almost instantaneous reduction to the 
metallic state, while the vapour of water, carried forward by the current of 
gas, escapes as a jet of steam from the extremity of the tube. In these 
experiments, the affinities between the iron and oxygen, and the hydrogen 
and oxygen, are so nearly balanced, that the difference of atmosphere is suf- 
ficient to settle the point. An atmosphere of steam offers little resistance 
to the escape of hydrogen ; one of hydrogen bears the same relation to steam ; 
and this apparently trifling difference of circumstances is quite enough for 
the purpose. 

The decomposition of vapour of water by white-hot platinum, pointed out 
by Mr. Grove, will probably be referred in great part to this influence of 
atmosphere, the steam offering great facilities for the assumption of the 
elastic condition by the oxygen and hydrogen. The decomposition ceases 
as soon as these gases amount to about l-3000th of the bulk of the mixture, 
and can only be renewed by their withdrawal. The attraction of uxygeu 
for hydrogen is probably much weakened by the very high temperature. The 
recombination of the gases by the heated metal is rendered impossible by 
their state of dilution. 

What is called the nascent state is one very favourable to chemical com- 
Di nation. Thus carbon and nitrogen refuse to combine with gaseous hy- 
16* 



186 PRINCIPLES OF CHEMICAL PHILOSOPHY. 

drogen ; yet -when these substances .are simultaneously liberated from some 
previous combination, they unite with great ease, as when organic matters 
are destroyed by heat, or by spontaneous putrefactive change. There is a 
strange and extraordinary, and at the same time very extensive class of 
actions, grouped together under the general title of cases of disposing affin- 
ity. The preparation of hydrogen from zinc and sulphuric acid is one of 
the most familiar. A piece of polished zinc or iron, put into pure water, 
manifests no power of decomposing the latter to the smallest extent ; it 
remains perfectly bright for any length of time. On the addition, however, 
of a little sulphuric acid, hydrogen is at once freely disengaged, and the 
metal becomes oxidized and dissolved. Now, the only intelligible function 
of the acid is to dissolve off the oxide as fast as it is produced ; but why is 
the oxide produced when acid is present, and not otherwise ? The question 
is very difficult to answer. 

Great numbers of examples of this curious indirect action might be 
adduced. Metallic silver does not oxidize at any temperature ; nay more, 
its oxide is easily decomposed by simple heat ; yet if the finely-divided metal 
be mixed with siliceous matter and alkali, and ignited, the whole fuses to a 
yellow transparent glass or silicate of silver. Platinum is attacked by fused 
hydrate of potassa ; hydrogen is probably disengaged while the metal is 
oxidized; this is an effect which never happens to silver under the same cir- 
cumstances, although silver is a much more oxidable substance than plati- 
num. The fact is, that potassa forms with the oxide of the last-named 
metal a kind of saline combination, in which the oxide of platinum acts as 
an acid; and hence its formation under the disposing influence of the power- 
ful base. 

In the remarkable decomposition suffered by various organic bodies when 
heated in contact with caustic alkali or lime, we have other examples of the 
same fact. Products are generated which are never formed in the absence 
of the base ; the reaction is invariably less complicated, and its results fewer 
in number and more definite, than in the event of simple destruction by a 
graduated heat. The preparation of light carbonetted hydrogen by the new 
artificial process, already described, is an excellent example. 

There is yet a still more obscure class of phenomena, in which effects are 
brought about by the mere presence of a substance, which itself undergoes 
no change whatever ; the experiment mentioned in the article on oxygen, 
in which that gas is obtained, with the greatest facility, by heating a mix- 
ture of chlorate of potassa and binoxide of manganese, is an excellent case 
in point. The salt is decomposed at a very far lower temperature than 
would otherwise be required. The oxide of manganese, however, is not in 
the slightest degree altered ; it is found, after the experiment, in the same 
state as before. The name katalysis is sometimes given to these peculiar 
actions of contact ; the expression is not significant, and may be for that 
reason the more admissible, as it suggests no explanation. 

It is proper to remark, that the contact-decompositions alluded to are 
sometimes mixed up with other effects, which are, in reality, much more in- 
telligible, as the action of finely-divided platinum upon certain gaseous mix- 
tures, in which the solid really seems to have the power of condensing the 
gas upon its greatly extended surface, and thereby inducing combination by 
bringing the particles within the sphere of their mutual attractions. 



CHEMISTRY OF THE VOLTAIC PILE. 1/7 



ELECTRO-CHEMICAL DECOMPOSITION; CHEMISTRY OF THE 
VOLTAIC PILE. 



When a voltaic current of considerable power is made to traverse various 
compound liquids, a separation of the elements of these liquids ensues ; pro- 
vided that the liquid be capable of conducting a current of a certain degree 
of energy, its decomposition almost always follows. 

The elements are disengaged solely at the limiting surfaces of the liquid ; 
where, according to the common mode of speech, the current enters and 
leaves the latter, all the intermediate portions appearing perfectly quiescent. 
In addition, the elements are not separated indifferently and at random at 
these two surfaces, but, on the contrary, make their appearance with per- 
fect uniformity and constancy at one or the other, according to their che- 
mical character, namely, oxygen, chlorine, iodine, acids, &c, at the surface 
connected with the copper or positive end of the battery ; hydrogen, the 
metals, &c, at the surface in connection with the zinc or negative extremity 
of the arrangement. 

The termination of the battery itself, usually, but by no means necessa- 
rily, of metal, are designated poles or electrodes, 1 as by their intervention 
the liquid to be experimented on is made a part of the circuit. The process 
of decomposition by the current is called electrolysis? and the liquids, which, 
when thus treated, yield up their elements, are denominated electrolytes. 

When a pair of platinum plates are plunged into a glass of water to which 
a few drops of oil of vitriol have been added, and the plates connected by 
wires with the extremities of an active battery, oxygen is disengaged at the 
positive electrode, and hydrogen at the negative, in the proportion of one 
measure of the former to two of the latter nearly. This experiment ha3 
before been described. 3 

A solution of hydrochloric acid mixed with a little Saxon blue (indigo), 
and treated in the same manner, yields hydrogen on the negative side, and 
chlorine on the positive, the indigo there becoming bleached. 

Iodide of potassium dissolved in water is decomposed in a similar man- 
ner, and with still greater ease ; the free iodine at the positive side can be 
recognized by its brown colour, or by the addition of a little gelatinous 
starch. 

Every liquid is not an electrolyte ; many refuse to conduct, and no decom- 
position can then occur ; alcohol, ether, numerous essential oils, and other 
products of organic chemistry, besides a few saline inorganic compounds, act 
in this manner, and completely arrest the current of a very powerful battery. 
It is a very curious fact, and well deserves attention, that very nearly, if not 
all the substances acknowledged to be susceptible of electrolytic decomposi- 
tion, belong to one class; they are all binary compounds, containing single 



1 From TjXeKrpov, and Wdf, a way. 
a 'From ri^etTpov, and \vu>, I loose. 
8 Page 115. 



183 ELECTRO-CHEMICAL DECOMPOSITION; 

equivalents of their components, the latter being strongly opposed to each 
other in their chemical relations, and held together by very powerful affinities. 

The amount of power required to effect decomposition varies greatly ; 
solution of iodide of potassium, melted chloride of lead, solution of hydro- 
chloric acid, water mixed with a little oil of vitriol, and pure water, demand 
in this respect very different degrees of electrical force, the resistance to 
decomposition increasing from the first-mentioned substance to the last. 

One of the most important and indispensable conditions of electrolysis is 
fluidity; bodies which when reduced to the liquid condition freely conduct 
and as freely suffer decomposition, become absolute insulators to the elec- 
tricity of the battery when they become solid. Chloride of lead offers a good 
illustration of this fact ; when fused in a little porcelain crucible it gives up 
its elements with the utmost ease, and a galvanometer, interposed somewhere 
in the circuit, is strongly affected. But when the source of heat is withdrawn, 
and the salt suffered to solidify, all signs of decomposition cease, and at the 
same moment the magnetic needle reassumes its natural position. In the 
same manner the thinnest film of ice completely arrests the current of a pow- 
erful voltaic apparatus ; the instant the ice is liquefied at any one point, so 
that water-communication may be restored between the electrodes, the cur- 
rent again passes, and decomposition occurs. Fusion by heat, and solution 
in aqueous liquids, answer the purpose equally well. A fluid substance may 
conduct a strong current of electricity without being decomposed ; there are 
a few examples already known ; the electrolysis of a solid is, from its physi- 
cal properties, of course out of the question. 

Liquids often exhibit the property of conduction for currents strong enough 
to be indicated by the galvanometer, but yet incapable of causing decompo- 
sition in the manner described. These currents may be conveyed through- 
extensive masses of liquids ; the latter seem, under these circumstances, to 
conduct after the manner of metals, without perceptible molecular change. 

The metallic terminations of the battery, the poles or electrodes, have, in 
themselves, nothing in the shape of attractive or repulsive power for the 
elements so often separated at their surfaces. Finely-divided metal suspended 
in water, or chlorine held in solution in that liquid, shows not the least 
symptom of a tendency to accumulate around them ; a single element is alto- 
gether unaffected, directly at least ; severance from that previous combination 
is required, in order that this appearance should be exhibited. 

It is necessary to examine the process of electrolysis a little more closely. 
When a portion of water, for example, is subjected to decomposition in a 
glass vessel with parallel sides, oxj'gen is disengaged at the positive electrode, 
and hydrogen at the negative ; the gases are perfectly pure and unmixed. 
If, while the decomposition is rapidly proceeding, the intervening water be 
examined by a beam of light, or by other means, not the slightest disturbance 
or movement of any kind will be perceived, nothing like currents in the liquid 
or bodily transfer of gas from one part to another can be detected, and yet 
two portions of water, separated perhaps by an interval of four or five inches, 
may be respectively evolving pure oxygen and pure hydrogen. 

There is, it would seem, but one mode of explaining this and all similar 
cases of regular electrolytic decomposition ; this is by assuming that all the 
particles of water between the electrodes, and by which the current is con- 
veyed, simultaneously suffer decomposition, the hydrogen travelling in one 
direction and the oxygen in the other. The neighbouring elements, thus 
brought into close proximity, unite and reproduce water, again destined to 
be decomposed by a repetition of the same change. In this manner each 
particle of hydrogen may be made to travel in one direction, by becoming 
successively united to each particle of oxygen between itself and the negative 
<yectrode ; when it reaches the latter, finding no disengaged particle of oxygen 



CHEMISTRY OF THE VOLTAIC PILE. 



189 



for its reception, it is rejected as it were from the series, and thrown off in 
a separate state. The same thing happens to each particle of oxygen, which 
at the same time passes continually in the opposite direction, by combining 
successively with each particle of hydrogen that mohient separated, with 
which it meets, until at length it arrives at the positive plate or wire, and is 
disengaged. A succession of particles of hydrogen are thus continually 
thrown off from the decomposing mass at one extremity, and a corresponding 
succession of particles of oxygen at the other. The power of the current is 
exerted with equal energy in every part of the liquid conductor, although its 
effects only become manifest at the very extremities. The action is one of a 

Fig. 125. 

Water in usual state. 

purely molecular or internal nature, and the metal terminations of the bat- 
tery merely serve the purpose of completing the connection between the 
latter and the liquid to be decomposed. The figures 125 and 126 are intended 
to assist the imagination of the reader, who must at the same time avoid re- 
garding them in any other light than that of a somewhat figurative mode of 
representing the curious phenomena described. The circles are intended to 
indicate the elements, and are distinguished by their respective symbols. 



Fig. 126. 




©(©)© 
©,© 



Water undergoing electrolysis. 

A distinction is to be carefully drawn between true and regular electro- 
lysis, and what is called secondary decomposition, brought about by the 
reaction of the bodies so eliminated upon the surrounding fluid, or upon the 
substance of the electrodes; hence the advantage of platinum for the latter 
purpose when electrolytic actions are to be studied in their greatest sim- 
plicity, that metal being scarcely attacked by any ordinary agents. When, 
for example, a solution of nitrate or acetate of lead is decomposed by the 
current between platinum plates, metallic lead is deposited at the negative 
side, and a brown powder, binoxide of lead, at the positive : the latter sub- 
stance is the result of a secondary action; it proceeds, in fact, from the 
nascent oxygen at the moment of its liberation reacting upon the protoxide 
of lead present in the salt, and converting it into binoxide, which is insoluble 
in the dilute acid. There is every reason to believe that when sulphuric 
and nitric acids seem to be decomposed by the current, the effect is really 
due to the water they contain becoming decomposed, and reacting by its 
hydrogen upon the acid ; for these bodies do not belong to the class of elec- 
trolytes, as already specified, and would probably refuse to conduct could 
they be examined in an anhydrous condition. 

If a number of different electrolytes, such as acidulated water, sulphate 
of copper, iodide of potassium, fused chloride of lead, &c, be arranged in a 



190 



ELECTRO-CHEMICAL DECOMPOSITION: 



Fig. 127. 



series, and the same current be made to traverse the whole, all will suffer 
decomposition at the same time, but by no means to the same amount. If 
arrangements be made by which the quantities of the eliminated elements 
can be accurately ascertained, it will be found, when the decomposition has 
proceeded to some extent, that these latter will have been disengaged exactly 
in the ratio of the chemical equivalents. The same current which decomposes 
9 parts of water will separate into their elements 1G6 parts of iodide of po- 
tassium, 139-2 parts of chloride of lead, &c. Hence the very important 
conclusion : The action of the current is perfectly definite in its nature, pro- 
ducing a fixed and constant amount of decomposition, expressed in each 
electrolyte by the value of its chemical equivalent. 

From a very extended series of experiments, based on this and other me- 
thods of research, Mr. Faraday was enabled to draw the general inference that 
effects of chemical decomposition were always proportionate to the quantity 
of circulating electricity, and might be taken as an accurate and trustworthy 
measure of the latter. Guided by this highly 
important principle, he constructed his voltame- 
ter, an instrument which has rendered the great- 
est service to electrical science. This is merely 
an arrangement by which a little acidulated 
water is decomposed by the current, the gas 
evolved being collected and measured. By plac- 
ing such an instrument in any part of the circuit, 
the quantity of electric force necessary to pro- 
duce any given effect can be at once estimated ; 
or, on the other hand, any required amount of 
the latter can be, as it were, measured out and 
adjusted to the object in view. The voltameter 
has received many different forms ; one of the 
most extensively useful is that shown in fig. 127, 
in which the platinum plates are separated by a 
very small interval, and the gas is collected in a graduated jar standing on 
the shelf of the pneumatic trough, the tube of the instrument, which is filled 
to the neck with dilute sulphuric acid, being passed beneath the jar. 

The decompositions of the voltaic battery can be effected by the electi-icity 
of the common machine, by that developed by magnetic action, and by that 
of animal origin, but to an extent incomparably more minute. This ai'ises 
from the very small quantity of electricity set in motion by the machine, 
although its tension, that is, power of overcoming obstacles, and passing 
through imperfect conductors, is exceedingly great. A pair of small wires 
of zinc and platinum, dipping into a single drop of dilute acid, develope far 
more electricity, to judge from the chemical effects of such an arrangement, 
than very many turns of a large plate electrical machine in high action. 
Nevertheless, polar or electrolytic decomposition can be distinctly and satis- 
factorily effected by the latter, although on a minute scale. 

With a knowledge of the principles laid down, the study of the voltaic 
battery may be resumed and completed. In the first place, two very different 
views have been held concerning the source of the electrical disturbance in 
that apparatus. Volta himself ascribed it to mere contact of dissimilar 
metals ; to what was denominated an electro-motive force, called into being 
by such contact ; the liquid merely serving the purpose of a conductor be- 
tween one pair of metals and that succeeding. Proof was supposed to be 
given of the fundamental position by an expei-iment in which discs of zinc 
and copper attached to insulating handles, after being brought into close 
contact, were found, by the aid of a very delicate gold-leaf electroscope, to 
be in opposite electrical states. It appears, however, that the more carefully 




CHEMISTRY OF THE VOLTAIC PILE. 



101 



Fie. 128. 




this experiment is made, the smaller is the effect observed ; and hence it is 
judged highly probable that the whole may be due to accidental causes, 
against which it is almost impossible to guard. 

On the other haud, the observation was soon made that the power of the 
battery always bore some kind of proportion to the chemical action upon the 
zinc ; that, for instance, when pure water was used the effect was extremely 
feeble ; with a solution of salt, it became much greater ; and, lastly, with 
dilute acid, greatest of all ; so that some relation evidently existed between 
the chemical effect upon the metal, and the evolution of electrical force. 

The experiments of Mr. Faraday and Professor Daniell have given very 
great support to the chemical theory, by showing that contact of dissimilar 
metals is not necessary in order to call into being powerful electrical currents, 
and that the development of electrical force is not only in 
pome way connected with the chemical action of the liquid of 
the battery, but that it is always in direct proportion to the 
latter. One very beautiful experiment, in which decompo- 
sition of iodide of potassium by real electrolysis is performed 
by a current generated without any contact of dissimilar 
metals, can be thus made: — A plate of zinc (fig. 128) is 
bent at a right angle, and cleaned by rubbing with sand- 
paper. A plate of platinum has a wire of the same metal 
attached to it by careful rivetting, and the latter bent into 
an arch. A piece of folded filter-paper is wetted with a so- 
lution of iodide of potassium, and placed upon the zinc ; the 
platinum plate is arranged opposite to the latter, with the 
end of its wire resting upon the paper, and then the pair 
plunged into a glass of dilute sulphuric acid, mixed with a 
few drops of nitric. A brown spot of iodine becomes in a moment evident 
beneath the extremity of the platinum wire; that is, at the positive side of 
the arrangement. 

A strong argument iu favour of the chemical view is founded on the easily- 
proved fact, that the direction of the current is determined by the kind of 
action upon the metals, the one least attacked being always positive. Let 
two polished plates, the one iron and the other copper, be connected by wires 
with a galvanometer, and then immersed in a solution of an alkaline sul- 
phide. The needle in a moment indicates a powerful current, passing from 
the copper, through the liquid, to the iron, and back again through the wire. 
Let the plates be now removed, cleaned, and plunged into dilute acid; the 
needle is again driven round, but in the opposite direction, the current now 
passing from the iron, through the liquid, to the copper. In the first instance 
the copper is acted upon, and not the iron ; in the second, these conditions 
are reversed, and with them the direction of the current. 

The metals employed in the practical construction of voltaic batteries are 
zinc for the active metal, and copper, silver, or, still better, platinum for the 
inactive one ; the greater the difference of oxidability, the better the arrange- 
ment. The liquid is either dilute sulphuric acid, sometimes mixed with a 
little nitric, or occasionally, where very slow and long-continued action is 
wanted, salt and water. To obtain the maximum effect of the apparatus 
with the least expenditure of zinc, that metal must be employed in a pure 
stale, or its surface must be covered by or amalgamated with mercury, which 
in its electrical relations closely resembles the pure metal. The zinc is easdy 
brought into this condition by wetting it with dilute sulphuric acid, and then 
rubbing a little mercury over it by means of a piece of rag tied to a stick 

The principle of the compound battery is, perhaps, best seen in the crown 
of cups ; by each alternation of zinc, fluid, and copper, the current is urged 
forwards with increased energy, its intensity is augmented, but the actual 



192 ELECTRO-CHE M IC A L 

amount of electrical force thrown into the current form is not increased. 
The quantity, estimated by its decomposing power, is, in fact, determined 
by that of the smallest and least active pair of plates, the quantity of elec- 
tricity in every part or section of the circuit being exactly equal. Hence 
large and small plates, batteries strongly and weakly charged, can never be 
connected without great loss of power. 

When a battery, either simple or compound, constructed with pure or with 
amalgamated zinc, is charged with dilute sulphuric acid, a number of highly 
interesting phenomena may be observed. While the circuit remains broken 
the zinc is perfectly inactive, no water is decomposed, no hydrogen liberated ; 
but the moment the connection is completed, torrents of hydrogen arise, 
not from the zinc, but from the copper or platinum surfaces alone, while the 
zinc undergoes tranquil and imperceptible oxidation and solution. Thus, 
exactly the same effects are seen to occur in every active cell of a closed 
circuit, which are witnessed in a portion of water undergoing electrolysis ; 
the oxygen appears at the positive side, with respect to the current, and the 
hydrogen at the negative ; but with this difference, that the oxygen, instead 
of being set free, combines with the zinc. It is, in fact, a real case of elec- 
trolysis, and electrolytes alone are available as exciting liquids. 

Common zinc is very readily attacked and dissolved by dilute sulphuric 
acid ; and this is usually supposed to arise from the formation of a multitude 
of little voltaic circles, by the aid of particles of foreign metals or plumbago, 
partially embedded in the zinc. This gives rise in the battery to what is 
called local action, by which in the common forms of apparatus three-fourths 
or more of the metal are often consumed, without contributing in the least 
to the general effect, but, on the contrary, injuring the latter to some extent. 
This evil is got rid of by amalgamating the surface. 

From experiments very carefully made with a "dissected" battery of 
peculiar construction, in which local action was completely avoided, it has 
been distinctly proved that the quantity of electricity set in motion by the 
battery varies exactly with the zinc dissolved. Coupling this fact with that 
of the definite action of the current, it will be seen, that when a perfect 
battery of this kind is employed to decompose water, in order to evolve 1 
grain of hydrogen from the latter, 83 grains of zinc must be oxidized and its 
equivalent quantity of hydrogen disengaged in each active cell of the battery. 
That is to say, that the electrical force generated by the oxidation of an 
equivalent of zinc in the battery, is capable of effecting the decomposition 
of an equivalent of water, or any other electrolyte out of it. 

This is an exceedingly important discovery; it serves to show in the most 
striking manner, the intimate nature of the connection between chemical and 
electrical forces, and their remarkable quantitative or equivalent relations. 
It almost seems, to use an expression of Mr. Faraday, as if a transfer of 
chemical force took place through the substance of solid metallic conductors ; 
that chemical actions, called into play in one portion of the circuit, could be 
made at pleasure to exhibit their effects without loss or diminution in any 
other. There is an hypothesis, not of recent date, long countenanced and 
supported by the illustrious Berzelius, which refers all chemical phenomena 
to electrical forces ; which supposes that bodies combine because they are in 
opposite electrical states ; even the heat and light accompanying chemical 
union may be, to a certain extent, accounted for in this manner. In short, 
we are in such a position, that either may be assumed as cause or effect ; it 
may be that electricity is merely a form or modification of ordinary chemical 
affinity ; or, on the other hand, that all chemical action is a manifestation 
of electrical force. 

One of the most useful forms of the common voltaic battery is that con- 
trived by Dr. Wollaston (fig. 129). The copper is made completely to encircle 



CHEMISTRY OF THE VOLTAIC PILE. 193 



Fig. 129. 




^w^^^a 




Fig. 130. 



the zmc ] late, except at the edges, the two metals being kept apart by pieces 
of cork or wood. Each zinc is soldered to the preceding copper, and the 
whole sciewed to a bar of dry mahogany, so that the plates can be lifted 
into or out of the acid, which is contained in an earthenware trough, divided 
into separate cells. The liquid consists of a mixture of 100 parts water*, 2\ 
parts oil of vitriol, and 2 parts commercial nitric acid, all by measure. A 
number of such batteries are easily connected together by straps of sheet 
copper, and admit of being put into action with great ease. 

The great objection to this and to all the older forms of the voltaic battery 
is, that the power rapidly decreases, so that after a short time scarcely the 
tenth part of the original action remains. This loss of power depends partly 
on the gradual change of the sulphuric acid into sulphate of zinc, but still 
more on the coating of hydrogen, and at a later stage, on the precipitation 
of metallic zinc on the copper plates. It is self-evident 
that if the copper plate in the fluid became covered 
with zinc, it would electrically, act like a zinc plate. 
This is precisely the action of the hydrogen, whereby 
a decrease of electrical power is produced. This effect, 
produced by the substances separated from the liquid, 
is commonly called polarization. 

An instrument of immense value for the purposes of 
electro-chemical research, in which it is desired to 
maintain powerful and equable currents for many suc- 
cessive hours, has been contrived by Professor Daniell 
(tig. 130). Each cell of this " constant" battery con- 
sists of a copper cylinder 3J inches in diameter, and 
of a height varying from 6 to 18 inches. The zinc is 
employed in the form of a rod f of an inch in diameter, 
carefully amalgamated, and suspended in the centre of 
the cylinder. A second cell of porous earthenware or 
animal membrane intervenes between the zinc and the 
copper ; this is filled with a mixture of 1 part by mea- 
sure of oil of vitriol and 8 of water, and the exterior 
space with the same liquid, saturated with sulphate of 
copper. A sort of little colander is fitted to the top of 
the cell, in which crystals of the sulphate of copper are placed, so that the 
17 



r 



194 



ELECTRO -CHEMICAL DECOMPOSITION; 



Tig. 131. 



strength of the solution may remain unimpaired. When a communication is 
made by a -wire between the rod and the cylinder, a powerful current is pro- 
duced, the power of which may be increased to any extent, by connecting a 
sufficient number of such cells into a series, on the principle of the crown 
of cups, the copper of the first being attached to the zinc of the second. 
Ten such alternations constitute a very powerful apparatus, which has the 
great advantage of retaining its energy undiminished for a lengthened period. 
For the copper plates become covered -with a compact precipitate of copper 
without tho evolution of any hydrogen, so long as the solution of sulphate 
of copper remains saturated. By this most excellent arrangement the sur- 
faces of the copper plates retain their original chemical properties unchanged. 
The polarization is avoided, and the chief cause of the gradual loss of powei 
is removed. 

Mr. Grove, on precisely the same principles, succeeded afterwards in form- 
ing a zinc and platinum battery, the action of which is con- 
stant. To hinder the evolution of hydrogen on the plati- 
num plates he employed the oxidizing action of nitric acid. 
One of the cells in this battery is represented in the 
margin, in section (fig. 131). The zinc plate is bent round,, 
so as to present a double surface, and well amalgamated ; 
within it stands a thin flat cell of porous earthenware, filled 
with strong nitric acid, and the whole is immersed in a 
mixture of 1 part by measure of oil of vitriol and 6 of 
water, contained either in one of the cells of Wollaston's 
trough, Dr in a separate cell of glazed porcelain, made for 
the purpose. The apparatus is completed by a plate of 
platinum foil which dips into the nitric a^id, and forms the 
positive side of the arrangement. With ten such pairs, 
experiments of decomposition, ignition of wires, the light 
between charcoal points, &c, can be exhibited with great 
brilliancy, while the battery itself is very compact and 
portable, and, to a great extent, constant in its action. The zinc, as in the 
case of 'Professor Daniell's battery, is only consumed while the current 
passes, so that the apparatus may be arranged an hour or two before it is 




required for use, which is often a matter of great convenience. 



The nitric 
acid suppresses the whole of the hydrogen, becoming thereby slowly deoxi- 
dized and converted into nitrous acid, which at first remains dissolved, but 
after some time begins to be disengaged from the porous cells in dense red 
fumes; this constitutes the only serious drawback to this excellent instru- 
ment. 

Professor Bunsen has modified the Grove battery by substituting for the 
platinum, dense charcoal or coke, which is an excellent conductor of elec- 
tricity. By this alteration, at a very small expense, a battery may be made 
as powerful and useful as that of Grove. On account of its cheapness, any 
one may put together one hundred or more of Bunsen's cells ; by which the 
most magnificent phenomena of heat and light may be obtained. 

Mr. Smee has contrived an ingenious battery, in which silver covered with 

thin coating of finely-divided metallic platinum is employed in association 
With amalgamated zinc and dilute sulphuric acid. The rough surface appears 
to permit the ready disengagement of the bubbles of hydrogen. 

Within the last nine or ten years, several very beautiful and successful 
applications of voltaic electricity have been made, which may be slightly 
mentioned. Mr. Spencer and Professor Jacobi have employed it in copying. 
or rather in multiplying, engraved plates and medals, by depositing upon 
their surfaces a thin coating of metallic copper, which, when separated from 
the original, exhibits, in reverse, a most faithful representation of the latter. 



CHEMISTRY OF THE VOLTAIC PILE 



195 



Fig. 132. 






n 



By using this in its turn as a mould or matrix, an absolutely perfect fac- 
simile of the plate or medal is cbtaiued. In the former case, 
the impressions taken on paper are cpiite indistinguishable from 
those directly derived from the work of the artist ; and as there 
is no limit to the number of electrotype plates which can be thus 
produced, engravings of the most beautiful description may be 
multiplied indefinitely. The copper is very tough, and bears 
the action of the press perfectly well. 

The apparatus used in this and many similar processes is 
of the simplest possible kind. A trough or cell of wood (fig. 
132) is divided by a porous diaphragm, made of a very thin 
piece of sycamore, into two parts; dilute sulphuric acid is put 
on one side, and a saturated solution of sulphate of copper, 
sometimes mixed with a little acid, on the other. A plate of 
zinc is soldered to a wire or strap of copper, the other end of 
which is secured by similar means to the engraved copper 
plate. The latter is then immersed in the solution of sulphate, 
and the zinc in the acid. To prevent deposition of copper on the back of 
the copper plate, that portion is covered with varnish. For medals and 
small works a porous earthenware cell, placed in a jelly-jar, may be used. 

Other metals may be precipitated in the same manner, in a smooth and 
compact form, by the use of certain precautions which have been gathered 
by experience. Electro-gilding and plating are now carried on very largely 
and in great perfection by Messrs. Elkington and others. Even non-conduct- 
ing bodies, as sealing-wax and plaster of Paris, may be coated with metal ; 
it is only necessary, as Mr. Murray has shown, to rub over them the thin- 
nest possible film of plumbago. Seals may thus be copied in a very few 
hours with unerring truth. 

M. Becquerel, several years ago, published an exceedingly intei'esting ac- 
count of certain experiments, in which crystallized metals, oxides, and other 
insoluble substances had been produced by the slow and continuous action 
of feeble electrical currents, kept up for months, or even years. These pro- 
ducts exactly resembled natural minerals, and, indeed, the experiments 
threw great light on the formation of the latter within the earth. 1 

The common but very pleasing experiment of the lead tree is greatly de- 
pendent on electro-chemical action. "When a piece of zinc is 
suspended in a solution of acetate of lead, the first effect is 
the decomposition of a portion of the latter, and the deposi- 
tion of metallic lead upon the surface of the zinc ; it is simply 
a displacement of a metal by a more oxidable one. The 
change does not, however, stop here ; metallic lead is still 
deposited in large and beautiful plates upon that first thrown 
down, until the solution becomes exhausted, or the zinc en- 
tirely disappears. (Fig. 133.) The first portions of lead form 
with the zinc a voltaic arrangement of sufficient power to de- 
compose the salt, under the peculiar circumstances in which 
the latter is placed, the metal is precipitated upon the nega- 
tive portion, that is, the lead, while the oxygen and acid are 
taken up by the zinc. 

Professor Grove has contrived a battery, in which an elec- 
ti'ical current, of sufficient intensity to decompose water, is produced by the 
reaction of oxygen upon hydrogen. Each element of this interesting appa- 
ratus consists of a pair of glass tubes to contain the gases, dipping into a 
vessel of acidulated water. Both tubes contain • platinum plates, covered 



Fig. 133 




Traite de l'Electricite et du Magnetismc, iii. 239. 



196 ELECTRO-CHEMICAL DECOMPOSITION. 

•with a rough deposit of finely-divided platinum, and furnished with conducting 
"wires, which pass through the tops or sides of the tubes, and are hermeti- 
cally sealed into the latter. "When the tubes are charged with oxygen on the 
one side and hydrogen on the other, and the wires connected with a galvano- 
scope. the needle of the instrument becomes instantly affected ; and when 
ten or more are combined in a series, the oxygen-tube of the one with the 
hydrogen-tube of the next, &c, while the terminal wires dip into acidulated 
water, a rapid stream of minute bubbles from either wire indicates the de- 
composition of the liquid ; and when the experiment is made with a small 
voltameter, it is found that the oxygen and hydrogen disengaged, exactly 
equal in amount the quantities absorbed by the act of combination in each 
tube of the battery. 



CHEMISTRY OF THE METALS. 197 



CHEMISTRY OF THE METALS, 



Tj\j vocals constitute the second and larger group of elementary bodies 
/ gveat amuler of these are of very rare occurrence, being found only in a 
ft jt sca\ ce mirerals ; others are more abundant, and some few almost uni- 
versally diffused throughout the whole globe. Some of these bodies are of 
most importance when in the metallic state ; others, when in combination, 
chiefly as oxides, the metals themselves being almost unknown. Many are 
used in medicine and in the arts, and are essentially connected with the pro- 
gress of civilization. 

If arsenic and tellurium be included, the metals amount to forty-nine in 
number. 

Physical Properties. — One of the most remarkable and striking characters 
possessed by the metals is their peculiar lustre ; this is so characteristic, that 
the expression metallic lustre has passed into common speech. This pro- 
perty is no doubt connected with the extraordinary degree of opacity which 
the metals present in every instance. The thinnest leaves or plates, the edges 
of crystalline larninas, arrest the passage of light in the most complete man- 
ner. An exception to this rule is usually made in favour of gold-leaf, which 
when held up to the daylight exhibits a greenish colour, as if it were really 
endued with a certain degree of translucency ; the metallic film is, however, 
always so imperfect, that it becomes difficult to say whether the observed 
effect may not be in some measure due to multitudes of little holes, many of 
which are visible to the naked eye. 

In point of colour, the metals present a certain degree of uniformity ; with 
two exceptions, viz. copper, which is red, and gold, which is yellow, all these 
bodies are included between the pure white of silver, and the bluish-grey 
tint of lead ; bismuth, it is true, has a pinkish colour, but it is very feeble. 

The differences of specific gravity are very wide, passing from potassium 
and sodium, which are lighter than water, to platinum, which is nearly 
twenty-one times heavier than an equal bulk of that fluid. 

Table of the Specific Gravities of Metals at 60° (15°-5C). 1 

Platinum 20-98 

Gold , 19-26 

Tungsten 17-60 

Mercury 13-57 

Palladium 11-30 to 11-8 

Lead 11-35 

Silver 10-47 

Bismuth 9-82 

Uranium 9 00 

Copper 8-89 

Cadmium 8-60 

1 Dr. Turner's Elements, eighth edition, p. 345. 
17* 



198 



CHEMISTRY OF THE METALS. 



Cobalt 8-54 

Nickel 8-28 

Iron 3-79 

Molybdenum 7-40 

Tin 7-29 

Zinc 7-86 to 7-1 

Manganese 685 

Antimony 6-70 

Tellurium 6-11 

Arsenic 5-88 

Aluminium 2-60* 

Magnesium 1-70 

Sodium 0-972 

Potassium 0-865 

The property of malleability, or power of extension under the hammer 
or between the rollers of the flatting-mill, is enjoyed by certain of the 
metals to a very great extent. Gold-leaf is a remarkable example of the 
tenuity to which a malleable metal may be brought by suitable means. The 
gilding on silver wire used in the manufacture of gold lace is even thinner, 
and yet presents an unbroken surface. Silver may be beaten out very thin ; 
copper also, but to an inferior extent ; tin and platinum are easily rolled out 
into foil ; iron, palladium, lead, nickel, cadmium, the metals of the alkalis, 
and mercury, when solidified, are also malleable. Zinc may be placed mid- 
way between the malleable and brittle division ; then perhaps bismuth, and, 
lastly, such metals as antimony and arsenic, which are altogether destitute 
of malleability. 

The specific gravity of malleable metals is usually very sensibly increased 
by pressure or blows, and the metals themselves rendered much harder, with 
a tendency to brittleness. This condition is destroyed and the former soft 
state restored by the operation of annealing, which consists in heating the 
metal to redness out of contact with air (if it will bear that temperature 
without fusion) and cooling it quickly or slowly according to the circum- 
stances of the case. After this operation it is found to possess its original 
specific gravity. 

Ductility is a property distinct from the last, inasmuch 
Fig. 134. as it involves the principle of tenacity, or power of re- 

sisting tension. The art of wire-drawing is one of great 
antiquity ; it consists in drawing rods of metal through a 
succession of trumpet-shaped holes in a steel plate (fig. 
134), each being a little smaller than its predecessor, until 
the requisite degree of fineness is attained. The metal 
often becomes very hard and rigid in this process, and is 
then liable to break ; this is remedied by annealing. The 
order of tenacity among the metals susceptible of being 
easily drawn into wire is the following : it is determined 
by observing the weights required to break asunder wires 
Irawn through tne same orifice of the plate : 




Iron 
Copper 
Platinum 
Silver 



Gold 
Zinc 
Tin 
Lead 



Metals differ as much in fusibility as in density ; the following table, ex- 



1 Wohler. 



CHEMISTRY OF THE METALS. 



199 



tracted from the late Dr. Turner's excellent work, -will give an idea of their 
relations to heat. The melting-points of the metals which only fuse at a 
temperature above ignition, and that of zinc, are on the authority of Mr. 
Daniell, having been observed by the help of the pyrometer before described : 

Meltini 
F. 

^Mercury '. — 39° - 

Potassium 136 

Sodium 194 

Tin 442 

Cadmium (about) 442 

Bismuth 497 

Lead 612 

Tellurium — rather less fusible than lead 
Arsenic — unknown 

Zinc 773 

Antimony — just below redness 

r Silver 1873 1022-77 

Copper 1996 1091-11 

Gold 2016 1102-22 

Cast iron... 2786 1530 



Fusible below 
a red heat 



; points. 
C. 

-39° -44 
57-77 
90 

227-77 
277-77 
258-33 
322-77 



411- 



Infusible below 
a red heat 



Pure iron " 

Nickel 

Cobalt 

Manganese. . 
Palladium .. 
Molybdenum . " 

Uranium 

Tungsten.... 
Chromium... 
Titanium .... 

Cerium 

Osmium 

Iridium 

Pthodium .... 
Platinum.... 
Tantalum J 



Fusible only in an excellent wind- 
furnace. 



Imperfectly melted in wind-furnace. 



Infusible in furnace ; fusible by oxy- 
hydrogen blowpipe. 



Some metals acquire a pasty or adhesive state before becoming fluid ; this 
is the case with iron and platinum, and also with the metals of the alkalis. 
It is this peculiarity which confers the very valuable property of welding, 
by which pieces of iron and steel are united without solder, and the finely- 
divided metallic sponge of platinum converted into a solid and compact bar. 

Volatility is possessed by certain members of this class, and perhaps by 
all, could temperatures sufficiently elevated be obtained. Mercury boils and 
distils below a red heat ; potassium, sodium, zinc, and cadmium, rise in 
vapour when heated to a bright redness ; arsenic and tellurium are volatile. 

CHEMICAL RELATIONS OF THE METALS ; CONSTITUTION OF SALTS. 

Metallic combinations are of two kinds ; namely, those formed by the 
union of metals among themselves, which are called alloys, or where mer- 
cury is concerned, amalgams, and those generated by combination with the 
non-metallic elements, as oxides, chlorides, sulphides, &c. In this latter 
case the metallic characters are very frequently lost. The alloys themselves 
are really true chemical compounds, and not mere mixtures of the consti- 



Oxygen. 


Symbols. Characters. 


1 eq. . 


.. MnO ... Strongly basic 


3 eq. . 


.. Mn 2 3 ... Feebly basic. 


2 eq. . 


.. Mn0 2 ... Neutral. 


3 eq. . 

7 eq. . 


" Mn 2 3 7 } Stron g^ acif *' 



200 CHEMISTRY OF THE 31 E T A L S . 

tuent metals ; their properties often differ completely from those of tho 
latter. 

The oxides of the metals may be divided, as already pointed out, into 
three classes ; namety, those which possess basic characters more or less 
marked, those -which refuse to combine with either acids or alkalis, and those 
which have distinct acid properties. The strong bases are all protoxides ; 
they contain single equivalents of metal and oxygen ; the weaker bases are 
usually sesquioxides, containing metal and oxygen in the proportion of two 
equivalents of the former to three of the latter ; the peroxides or neutral 
compounds are still richer in oxygen, and, lastly, the metallic acids contain 
the maximum proportion of that element. 

The gradual change of properties by increasing proportions of oxygen is 
well illustrated by the case of manganese. 

Metal. 

Protoxide 1 eq. 

Sesquioxide 2 eq. 

Binoxide 1 eq. 

Manganic acid 1 eq. 

Permanganic acid 2 eq. 

The oxides of iron and chromium present similar, but less numerous gra- 
dations. 

When a powerful oxygen-acid and a powerful metallic base are united in 
such proportions that they exactly destroy each other's properties, the re- 
sulting salt is said to be neutral ; it is incapable of affecting vegetable 
colours. Now, in all these well-characterized neutral salts, a constant and 
very remarkable relation is observed to exist between the quantity of oxygen 
in the base, and the quantity of acid in the salt. This relation is expressed 
in the following manner : — To form a neutral combination, as many equiva- 
lents of acid must be present in the salt as there are of oxygen in the base 
itself. In fact, this has become the very definition of neutrality, as the 
action on vegetable colours is sometimes an unsafe guide. 

It is easy to see the application of this law. When a base is a protoxide, 
a single equivalent of acid suffices to neutralize it ; when a sesquioxide, not 
less than three are required. Hence, if by any chance, the base of a salt 
should pass by oxidation from the one state to the other, the acid will be in- 
sufficient in quantity by one-half to form a neutral combination. Sulphate 
of the protoxide of iron offers an example ; when a solution of this substance 
is exposed to the air, it absorbs oxygen, and a yellow insoluble sub-salt, or 
b-isic-salt, is produced, which contains an excess of base. Four equivalents 
of the green compound absorb from the air two equivalents of oxygen, and 
give rise to one equivalent of neutral and one equivalent of basic sulphate 
of the sesquioxide, as indicated by the diagonal zigzag line of division. 

1 eq. iron -f- 1 eq. oxygen 1 eq. sulphuric acid. 

1 eq. iron -j- 1 eq. oxygen 1 eq. sulphuric acid. 

| -f- 1 eq. oxygen from air 

1 eq. iron 4- 1 eq. oxygen I 1 eg. sulphuric acid. 

1 eq. iron -j- 1 eq. oxygen 1 eq. sulphuric acid. 

~\- 1 eq. oxygen from air. 

Such sub-salts or basic salts are very frequently insoluble. 

The combinations of chlorine, iodine, bromine, and fluorine with the petals 
possess in a very high degree the saline character. If, however, the definition 
formerly given of a salt be rigidly adhered to, these bodies must be excluded 
from the class, and with them the very sixbstance from which the name is 



CHEMISTRY OF THE METALS. £01 

derived, that is, common salt, which is a chloride of sodium To obviate 
this anomaly, it has been found necessary to create two classes of salts ; in 
the first division will stand those constituted after the type of common salt, 
which contain a metal and a salt-radical, as chlorine, iodine, &c. ; and in the 
second, those which, like sulphate of soda and nitrate of potassa, are gene- 
rally supposed to be combinations of an acid with an oxide. The names 
haloid 1 salts, and oxygen-acid, or oxy-salts, are given to these two kinds. 

When a haloid salt is dissolved in water, it might be regarded as a combi- 
nation of a metallic oxide with a hydrogen-acid, the water being supposed 
to undergo decomposition, its hydrogen being transferred to the salt-radical, 
and its oxygen to the metal. This view is unsupported by evidence of any 
value : it is much more probable, indeed, that no truly saline compounds of 
hydrogen-acids exist, at any rate in inorganic chemistry. When a solution 
of any hydrogen-acid is poured upon a metallic oxide, we may rather suppose 
that both are decomposed, water and a haloid salt of the metal being pro- 
duced. Take hj^drochloric acid and potassa by way of example. 

Hydrochloric f Chlorine -—^ Chloride of potassium. 

acid \ Hydrogen ^^^ — 

Potassa jPotassium-^^^^ 

I Oxygen ^-^ Water# 

On evaporating the solution, the chloride of potassium crystallizes out. 

When hydrochloric acid and ammoniacal gases are mixed, they combine 
with some energy and form a white solid salt, sal-ammoniac. Now this sub- 
stance bears such a strong resemblance in many important particulars to 
chloride of potassium and common salt, that the ascription to it of a similai 
constitution is well warranted. 

If chloride of potassium, therefore, contain chlorine and metal, sal-ammo- 
niac may also contain chlorine in combination with a substance having the 
chemical relations of a metal, formed by the addition of the hydrogen of the 
acid to the elements of the ammonia. 

Hydrochloric f 1 eq. Chlorine Chlorine ... "1 

acid \1 eq. Hydrogen g a j. 

Ammonia ... i ? eq " S dr0Sen ^^-^ I ammoniac. 

\1 eq. Nitrogen —^2^ Ammonium J 

The term ammonium is given to this hypothetical body, NH 4 ; it is sup- 
posed to exist in all the ammoniacal salts. Thus we have chloride of 
ammonium, sulphate of the oxide of ammonium, &c. This view is very 
strongly supported by the peculiarities of the salts themselves, and by the 
existence of a series of substances intimately related to these salts in organic 
chemistry, as will hereafter be seen. 

Many of the sulphides also possess the saline character and are soluble in 
water, as those of potassium and sodium. Sometimes a pair of sulphides 
will unite in definite proportions, and form a crystallizable compound. Such 
bodies bear a very close resemblance to oxygen-acid salts ; they usually 
contain a protosulphide of an alkaline metal, and a higher sulphide of a non- 
metallic substance or of a metal which has little tendency to form a basic 
oxide, the two sulphides having exactly the same relation to each other as 
the oxide and acid of an ordinary salt. Hence the expressions sulphur-salt, 
sulphur-acid, and sulphur-base, which Berzelius applies to such compounds ; 
they contain sulphur in the place of oxygen. Thus, bisulphide of carbon is 
a sulphur-acid ; it forms a crystallizable compound with protosulphide of 
potassium, which is a sulphur-base. Were oxygen substituted for the sulphur 
in this product, we should have carbonate of potassa. 

* (iXf, sea-salt, and eldos, form. 



% 2 CHEMISTRY OF THE METALS. 

KS-f CS 2 sulphur-salt. 
KO-|-C0 2 oxygen-salt. 

These remarkable compounds are very numerous and interesting ; they 
have been studied by Berzelius with great care. 

Salts often combine together, and form what are called double salts, in 
which the same acid is in combination with two different bases. When sul- 
phate of copper and sulphate of potassa, or chloride of zinc and sal-ammoniac, 
are mixed in the ratio of the equivalents, dissolved in water, and the solution 
made to crystallize, double salts are obtained. These latter are often more 
beautiful, and crystallize better than their constituent salts. 

Many of the compounds called super, or acid salts, such as bisulphate of 
potassa, which have a sour taste and acid reaction to test-paper, ought 
strictly to be considered in the light of double salts, in which one of the 
bases is water. Strange as it may at first sight appear, water possesses 
considerable basic powers, although it is unable to mask acid reaction on 
vegetable colours ; hydrogen, in fact, very much resembles a metal in its 
chemical relations. Bisulphate of potassa will, therefore, be a double sul- 
phate of potassa and water, while oil of vitriol must be assimilated to neutral 
sulphate of potassa. 

KO-fS0 3 andHO+S0 3 . 

"Water is a weak base ; it is for the most part easily displaced by a metallic 
oxide ; yet cases occur now and then in which the reverse happens, and 
water is seen to decompose a salt, in virtue of its basic power. 

There are few acid salts which contain no water ; as the bichromate of 
potassa, and a new anhydrous sulphate of potassa discovered by M. Jaque- 
lain. 1 It will be necessary, of course, to adopt some other view in these 
cases. The simplest will be to consider them as really containing two equi- 
valents of acid to one of base. 

By water of crystallization is meant water in a somewhat loose state of com- 
bination with a salt, or other compound body, from which it can be disen- 
gaged by the mere application of heat, or by exposure to a dry atmosphere. 
Salts which contain water of crystallization have their crystalline form greatly 
influenced by the proportion of the latter. Green sulphate of iron crystal- 
lizes in two different forms, and with two different proportions of water, 
according to the temperature at which the salt separates from the solution. 

Many salts containing water effloresce in a dry atmosphere, crumbling to 
powder, and losing part or the whole of their water of crystallization ; while 
in a moist atmosphere they may be preserved unchanged. The opposite 
effect to this, or deliquescence, results from a strong attraction of the salt for 
water, in virtue of which it absorbs the latter from the air, often to the 
extent of liquefaction. 

Crystallization; Crystalline Forms. — Almost every substance, simple and 
compound, capable of existence in the solid state, assumes, under favourable 
circumstances, a distinct geometrical form or figure, usually bounded by 
plane surfaces, and having angles of fixed and constant value. The faculty 
of crystallization seems to be denied only to a few bodies, chiefly highly 
complex organic principles, which stand, as it were, upon the very edge of 
organization, and which, when in a solid state, are frequently characterized 
by a kind of beady or globular appearance, well known to microscopical 
observers. 

The most beautiful examples of crystallization are to be found among 
natural minerals, the result of exceedingly slow changes constantly occurring 
within the earth; it is invariably found that artificial crystals of salts, and 

1 Ann. Chim. et Hiys. Ixx. 311. 



CHEMISTRY OF THE METALS. 



203 



other soluble substances, which have been slowly and quietly deposited, 
always surpass in size and regularity those of more rapid formation. 

Solution in water or some other liquid is one very frequent method of 
effecting crystallization. If the substance be more soluble at a high than at 
a lower temperature, then a hot and saturated solution by slow cooling will 
generally be found to furnish crystals ; this is a very common case with salts 
and various organic principles. If it be equally soluble, or nearly so, at all 
temperatures, then slow spontaneous evaporation in the air, or over a sur- 
face of oil of vitriol, often proves very effective. 

Fusion and slow cooling may be employed in many cases ; that of sulphur 
s a' good example ; the metals usually afford traces of crystalline figure 
when thus treated, which sometimes become very beautiful and distinct, as 
with bismuth. A third condition under which crystals very often form is in 
passing from a gaseous to a solid state, of which iodine affords a good in- 
stance. When by any of these means time is allowed for the symmetrical 
arrangement of the particles of matter at the moment of solidification, 
crystals are produced. 

That crystals owe their figure to a certain regularity of internal structure, 
is shown both by their mode of formation and also by the peculiarities at- 
tending their fracture. A crystal placed in a slowly-evaporating saturated 
solution of the same substance grows or increases by a continued deposition 
of fresh matter upon its sides in such a manner that the angles formed by 
the meeting of the latter remain unaltered. 

The tendency of most crystals to split in particular directions, called by 
mineralogists cleavage, is a certain indication of regular structure, while the 
curious optical properties of many among them, and their remarkable mode 
of expansion by heat, point to the same conclusion. 

It may be laid down as a general rule that every substance has its own 
crystalline form, by which it may very frequently be recognized at once ; 
not that each substance has a different figure, although very great diversity 
in this respect is to be found. Some forms are much more common than 
others, as the cube and six-sided prism, which are very frequently assumed 
by a number of bodies, not in any way related. 

The same substance may have, under different sets of circumstances, as 
high and low temperatures, two different crystalline forms, in which case it 
is said to be dimorphous. Sulphur and carbon furnish, as already noticed, 
examples of this curious fact ; another case is presented by carbonate of 
lime in the two modifications of calcareous spar and arragonite, both chemi- 
cally the same, but physically different. A fourth example might be given 
in the iodide of mercury, which also has two distinct forms, and even two 
distinct colours, offering as great a contrast as those of diamond and plum- 
bago. 

Fig. 135. 





204 



CHEMISTRY OF THE METALS, 



The angles of crystals are measured by means of instruments called goni- 
ometers, of which there are two kinds in use, namely, the old or common 
goniometer, and the reflective goniometer of Dr. Wollaston. 

The common goniometer consists of a pair of steel blades moving with 
friction upon a centre, as shown in the cut (fig. 135). The edges a a are 
carefully adjusted to the faces of the crystal, whose inclination to each other 
it is required to ascertain, and then the instrument being applied to the di- 
vided semicircle, the contained angle is at once read off. An approximative 
measurement, within one or two degrees, can be easily obtained by this in- 
strument, provided the planes of the crystal be tolerably perfect, and large 
enough for the purpose. Some practice is of course required before even 
this amount of accuracy can be attained. 

The reflective goniometer is a very superior instrument, its indications be- 
ing correct within a fraction of a degree ; it is applicable also to the mea- 
surement of the angles of crystals of very small size, the only condition 
required being that their planes be smooth and brilliant. The subjoined 
sketch (fig. 136) will convey an idea of its nature and mode of use. 

Fig. 136. 




a is a divided circle or disc of brass, the axis of which passes stiffly and 
without shake through the support b. This axis is itself pierced to admit 
the passage of a round rod or wire, terminated by the milled-edged head c, 
and destined to carry the crystal to be measured by means of the jointed 
arm d. A vernier, e, immovably fixed to the upright support, serves to mea- 
sure with great accuracy the angular motion of the divided circle. The 
crystal at / can thus be turned round, or adjusted in any desired position, 
without the necessity of moving the disc. 

The principle upon which the measurement of the angle rests is very 
simple. If the two adjacent planes of a crystal be successively brought into 
the same position, the angle through which the crystal will have moved will 
be the supplement to that contained between the two planes. This will be easily 
intelligible by reference to fig. 137, in which a crystal having the form of a 
triangular prism ' is shown in the two positions, the angle to be measured 
being that indicated by the letters e df. 

The lines a c, be, are perpendicular to the respective faces of the crystal, 



1 The triangular prism has heen chosen for the sake of simplicity; hut a moment's con- 
sideration will show that the rule applies equally well to any other figure. 



CHEMISTRY OF THE METALS. 



205 



Pig. 137. 



6'' 





consequently the internal angles dg c, dhc, are right angles. Now, sinco 
the sum of the internal angles of a four-sided rectilineal figure, as dgck, 
equal four right angles, or 860°, the angle gdh (or e df) must of necessity 
he the supplement to the angle g c h, or that through which the crystal 
moves. All that is required to he done, therefore, is to measure the latter 
angle with accuracy, and subtract its value from 180° ; and this the gonio- 
meter effects. 

One method of using the instrument is the following : — The goniometer is 
placed at a convenient height upon a steady table in front of a well-illumi- 
nated window. Horizontally across the latter, at the height of eight or nine 
feet from the ground, is stretched a narrow black ribbon, while a second 
similar ribbon, adjusted parallel to the first, is fixed beneath the window, a 
foot or eighteen inches above the floor. The object is to obtain too easily- 
visible black lines, perfectly parallel. The crystal to be examined is attached 
to the arm of the goniometer at / by a little wax, and adjusted in such a 
manner that the edge joining the two planes whose inclination is to be mea- 
sured shall nearly coincide with, or be parallel to, the axis of the instru- 
ment. This being done, the adjustment is completed in the following manner: 
— The divided circle is turned until the zero of the vernier comes to 180° ; 
the crystal is then moved round by means of the inner axis c (fig. 136) until 
the eye placed near it perceives the image of the upper black line reflected 
from the surface of one of the planes in question. Following this image, 
the crystal is still cautiously turned until the upper black line seen by re- 
flection approaches and overlaps the lower black line seen directly by another 
portion of the pupil. It is obvious, that if the plane of the crystal be quite 
parallel to the axis of the instrument (the latter being horizontal), the two 
lines will coincide completely. If, however, this should not be the case, the 
crystal must be moved upon the wax until the two lines fall in one when su- 
perposed. The second face of the crystal must then be adjusted in the same 
manner, care being taken not to derange the position of the first. When by 
repeated observation it is found that both have been correctly placed, so as 
to bring the edge into the required condition of parallelism with the axis of 
motion, the measurement of the angle may be made. 

For this purpose the crystal is moved as before by the inner axis until the 
image of the upper line, reflected from the first face of the crystal, covers 
the lower line seen directly. The great circle, carrying the whole with it, 
is then cautiously turned until the same coincidence of the upper with the 
lower line is seen by means of the second face of the crystal ; that is, the 
second face is brought into exactly the same position as that previously 
occupied by the first. Nothing then remains but to read off by the vernier 
the angle through which the circle has been moved in this operation. The 
division upon the circle itself is very often made backwards, so that the 
18 



206 



CHEMISTRY OF THE METALS, 



angle of motion is not obtained, but its supplement, or the angle of the 
crystal required. 

It may be necessary to remark, that, although the principle of the opera- 
tion described is in the highest degree simple, its successful practice requires 
considerable skill and experience. 

If a crystal of tolerably simple form be attentively considered, it -will be- 
come evident that certain directions can be pointed out in which straight 
lines may be imagined to be drawn, passing through the central point of the 
crystal from side to side, from end to end, or from one angle to that opposed 
o it, &c, about which lines the particles of matter composing the crystal 
may be conceived to be symmetrically built up. Such lines or axes are not 
always purely imaginary, however, as may be inferred from the remarkable 
optical properties of many crystals : upon their number, relative lengths, 
position, and inclination to each other, depends the outward figure of the 
crystal itself. 

All crystalline forms may upon this plan be arranged in six classes or 
systems ; these are as follows : — 

1. The regular system. — The crystals of this division have three equal axes, 
all placed at right angles to each other. The most important forms are the 
cube (1), the regular octahedron (2), and the rhombic dodecahedron (3). 

The letters a — a show the terminations of the three axes, placed as stated. 




Very many substances, both simple and compound, assume these forms, as 
most of the metals, carbon in the state of diamond, common salt, iodide of 
potassium, the alums, fluor-spar, bisulphide of iron, garnet, spinelle, &c. 

2. The square prismatic system. — Three axes are here also observed, at 
right-angles to each other. Of these, however, two only are of equal length, 
the third being usually longer or shorter. The most important forms are : 
a right square prism, in which the latter axes terminate in the central point 



riff. 13 




/. a, 










i 
7 


• 




a — a. Principal, or vertical axis. 
b — b. Secondary, or lateral axis. 



CHEMISTRY OF THE METALS. 



207 



of each side (1) ; a second right square prism, in which the axes terminate in 
the edges (2) ; a corresponding pair of right square-based octahedra (3 and 4). 

Examples of these forms are to be found in zircon, native binoxide of tin, 
apophyllite, yellow ferrocyanide of potassium, &c. 

3. The right prismatic system. — This is characterized by three axes of un- 
equal lengths, placed at right-angles to each other, as in the right rectangular 
prism (1), the right rhombic prism (2), the right rectangular-based octahedron, 
(3), and the right rhombic-based octahedron (4). 




a — a. Principal axis. 

b — b, c — c. Secondary axes. 

The system is exemplified in sulphur crystallised at a low temperature, 
arsenical iron pyrites, nitrate and sulphate of pptassa, sulphate of baryta, &c. 

4. The oblique prismatic si/stem. — Crystals belonging to this group have also 
three axes which may be all unequal, two of these (the secondary) are placed 
at right angles, the third being so inclined as to be oblique to one and per- 
pendicular to the other. To this system may be referred the four following 




a— a. Principal axis. 

b — b, c c. Secondary axes. 

form3 : — The oblique rectangidar prism (1), the oblique rhombic prism (2), the 
oblique rectangular-based octahedron (3), the oblique rhombic-based octahe- 
dron (4). 

Such forms are taken by sulphur crystallized by fusion and cooling, real- 
gar, sulphate, carbonate and phosphate of soda, borax, green vitriol, and 
many other salts. 

5. The doubly -oblique prismatic system. — The crystalline forms comprehended 
in this division are, from their great apparent irregularity, exceedingly dif- 
ficult to studv and understand. In them are traced three axes, which may 



>08 



CHEMISTRY OF THE METALS. 



be all unequal in length, and are all oblique to each other, as in the two 
doubly-oblique prisms (1 and 2), and in the corresponding doubly -oblique octa- 
hedrons (3 and 4). 

Fig. 142. 




a — a. Principal axis, as before. 
b — b, c — c. Secondary axes. 

Sulphate of copper, nitrate of bismuth, and quadroxalate of potassa, afford 
illustrations of these forms. 

6. The rhombohedral system. — This is very important and extensive : it is 
characterized by the presence of four axes, three of -which are equal, in the 
same plane, and inclined to each other at angles of 60°, while the fourth or 

Fig. 143. 



V 


pz-l 


7,. 


**, 


U-i 


V 


< 


a 


y 




a — a. Principal axis. 
b — 6. Secondary axes. 

principal axis is perpendicular to all. The regular six-sided prism (1), th«> 
quartz- dodecahedron (2), the rhombohedron (3), and a second dodecahedron, 
whose faces are scalene triangles (4), belong to the system in question. 

Examples are readily found ; as in ice, calcareous spar, nitrate of soda, 
beryl, quartz or rock crystal, and the semi-metals, arsenic, antimony, and 
tell>rium. 

If a crystal increase in magnitude by equal additions on every part, it is 
quite clear that its figure must remain unaltered; but, if from some cause 
this increase should be partial, the newly-deposited matter being distributed 
unequally, but still in obedience to certain definite laws, then alterations of 
form are produced, giving rise to figures which have a direct geometrical 
connection with that from which they are derived. If, for example, in the 
cube, a regular omission of successive rows of particles of matter in a cer- 
tain order be made at each solid angle, while the crystal continues to increase 
elsewhere, the result will be the production of small triangular planes, 



CHEMISTRY OF THE METALS. 



209 



■which, as the process advances, gradually usurp the -whole of the surface of 
the crystal, and convert the cube into an octahedron. The new plane3 are 
called secondary, and their production is said to take place by regular decre- 
ments upon the solid angles. The same thing may happen on the edges of 
the cube ; a new figure, the rhombic dodecahedron, is then generated. Fig. 
144. The modifications which can thus be produced of the original or 
primary figure (all of which are subject to exact geometrical laws) are very 
numerous. Several distinct modifications may be present at the same time, 
and thus render the form exceedingly complex. 

Fig. 144. 




Passage of cube to octahedron. 

It is important to observe, that in all these deviations from what may be 
regarded as the pi'imary or fundamental figure of the crystal, the modifying 
planes are in fact the planes of figures belonging to the same natural group or 
crystallographical system as the primary form, and having their axes coincident 
xoith those of the latter. The crystals of each system are thus subject to a 
peculiar and distinct set of modifications, the observation of which very 
frequently constitutes an excellent guide to the discovery of the primary 
form itself. 

Crystals often cleave parallel to all the planes of the primary figure, as in 
calcareous spar, which offers a good illustration of this perfect cleavage. 
Sometimes one or two of these planes have a kind of preference over the 
rest in this respect, the crystal splitting readily in these directions only. 

A very curious modification of the figure sometimes occurs by the exces- 
sive growth of each alternate plane of the crystal ; the rest become at length 
obliterated, and the crystal assumes the character called hemihedral or half- 
sided. This is well seen in the production of the tetrahedron from the regular 
octahedron (fig. 145), and of the rhombohedric form by a similar change 
from the quartz-dodecahedron already figured. 

Fig. 145. 




Passage of octahedron to tetrahedron. 



Relations of form and constitution ; Isomorphism. — Certain substances to 
which a similar chemical constitution is ascribed, possess the remarkable 
property of exactly replacing each other in crystallized compounds without 
alteration of the characteristic geometrical figure. Such bodies are said to 
be isomorphous. 1 



18* 



1 from tVoj, equal, and y.6p<prj, shape or form. 



210 CHEMISTRY OP THE METALS. 

For example, magnesia, oxide of zinc, oxide of copper, protoxide of iron, 
and oxide of nickel, are allied by isomorphic relations of the most intimate 
nature. The salts formed by these substances with the same acid and 
similar proportions of water of crystallization, are identical in their form, 
and, when of the same colour, cannot be distinguished by the eye ; the sul- 
phates of magnesia and zinc may be thus confounded. The sulphates, too, 
all combine with sulphate of potassa and sulphate of ammonia, giving rise 
to double salts, whose figure is the same, but quite different from that of the 
simple sulphates. Indeed, this connection between identity of form and 
parallelism of constitution runs through all their combinations. 

In the same manner, alumina and sesquioxide of iron replace each other 
continually without change of crystalline figure ; the same remark may be 
made of potassa, soda, and ammonia, with an equivalent of water, or oxide 
of ammonium, these bodies being strictly isomorphous. The alumina in 
in common alum may be replaced by sesquioxide of iron ; the potassa by 
ammonia, or by soda, and still the figure of the crystal remains unchanged. 
These replacements may be partial only; we may have an alum containing 
both potassa and ammonia, or alumina and sesquioxide of chromium. By 
artificial management, namely, by transferring the crystal successively to 
different solutions, we may have these isomorphous and mutually replacing 
compounds distributed in different layers upon the same crystal. 

For these reasons, mixtures of isomorphous salts can never be separated 
by crystallization, unless their difference of solubility is very great. A 
mixed solution of sulphate of protoxide of iron and sulphate of copper, iso- 
morphous salts, yields on evaporation crystals containing both iron and 
copper. But if before evaporation the protoxide of iron be converted into 
sesquioxide by chlorine or other means, then the crystals obtained are free 
from iron, excapt that of the mother-liquor which wets them. The salt of 
sesquioxide of iron is no longer isomorphous with the copper salt, and easily 
separates from the latter. 

When compounds are thus found to correspond, it is inferred that the ele- 
ments composing them are also isomorphous. Thus, the metals magnesium, 
zinc, iron, and copper are presumed to be isomorphous; arsenic and phos- 
phorus should present the same crystalline form, because arsenic and phos- 
phoric acids give rise to combinations which agree most completely in figure 
and constitution. The chlorides, iodides, bromides, and fluorides, agree, 
whenever they can be observed, in the most perfect manner ; hence the ele- 
ments themselves are believed to be also isomorphous. Unfortunately, for 
obvious reasons, it is very difficult to observe the crystalline figure of most 
of the elementary bodies, and this difficulty is increased by the frequent di- 
morphism they exhibit. 

Absolute identity of value in the angles of crystals is not always exhibited 
by isomorphous substances. In other words, small variations often occur 
in the magnitude of the angles of crystals of compounds which in all other 
respects show the closest isomorphic relations. This should occasion no 
surprise, as there are reasons why such variations may be expected, the 
chief perhaps being the unequal effects of expansion by heat, by which the 
angles of the same crystals are changed by alteration of temperature. A 
good example is found in the case of the carbonates of lime, magnesia, man- 
ganese, iron, and zinc, which are found native crystallized in the form of 
obtuse rhombohedra (fig. 143, 3) not distinguishable from each other by the 
eye, or even by the common goniometer, but showing small differences when 
examined by the more accurate instrument of Dr. Wollaston. These com- 
pounds are isomorphous, and the measurements of the obtuse angles of theii 
rhombohedra as follows : — 



CHEMISTRY OF THE METALS. 



211 



Carbonate of lime 105° 5 / 

" magnesia 107° 25 / 

" protox. manganese 107° 20' 

" " iron 107° 

zinc 107° 40' 

Anomalies in the composition of various earthy minerals which formerly 
threw much obscui-ity upon their chemical nature, have been in great mea- 
sure explained by these discoveries. 

Specimens of the same mineral from different localities were found to 
afford very discordant results on analysis. But the proof once given of the 
extent to which substitution of isomorphous bodies may go without destruc- 
tion of what may be called the primitive type of the compound, these diffi- 
culties vanish. 

Another benefit conferred on science by the discoveries in question, is 
that of furnishing a really philosophical method of classifying elementary 
and compound substances, so as to exhibit their natural relationships : it 
would be perhaps more proper to say that such will be the case when the 
isomorphic relations of all the elementary bodies become known, — at present 
only a certain number have been traced. 

Decision of a doubtful point concerning the constitution of a compound 
may now and then be very satisfactorily made by a reference to this same 
law of isomorphism. Thus, alumina, the only known oxide of aluminium, 
is judged to be a sesquioxide of the metal from its relation to sesquioxide 
of iron, which is certainly so ; the black oxide of copper is inferred to be 
really the protoxide, although it contains twice as much oxygen as the red 
oxide, because it is isomorphous with magnesia and zinc, both undoubted 
protoxides. 

The subjoined table will serve to convey some idea of the most important 
families of isomorphous elements ; it is taken from Professor Graham's sys- 
tematic work, 1 to which the pupil is referred for fuller details on this inte- 
resting subject. 

Isomorphous Groups. 

(1.) (3.) (7.) 

Sulphur Barium Sodium 

Selenium * Strontium Silver 

Tellurium. Lead. Gold 

(2.) (4.) Potassium 

Magnesium Tin Ammonium. 

Calcium Titanium. (8.) 

Manganese (5.) Chlorine 

Iron Platinum Iodine 

Cobalt Iridium Bromine 

Nickel Osmium. Fluorine 

Zinc (6.) Cyanogen. 

Cadmium Tungsten (9.) 

Copper Molybdenum Phosphorus 

Chromium Tantalum. Arsenic 

Aluminium Antimony 

Beryllium BismuthI 
Vanadium 
Zirconium. 
There is a law concerning the formation of double salts which may now 
be mentioned ; the two bases are never taken from the same isomorphous 

1 Second edition, p. 149. 



212 CHEMISTRY OF THE METALS. 

family. Sulphate of copper or of zinc may unite in this manner with sulphate 
of soda or potassa, but not with sulphate of iron or cobalt; chloride of mag- 
nesium may combine with chloride of ammonium, but not with chloride of 
zinc or nickel, &c. It will be seen hereafter that this is a matter of some 
importance in the theory of the organic acids. 

Polybasic Acids. — There is a particular class of acids in which a departure 
occurs from the law of neutrality formerly described ; these are acids re- 
quiring two or more equiyalents of a base for neutralization. The phosphoric 
and arsenic acids present the best examples yet known in mineral chemistry, 
but in the organic department of the science cases very frequently occur. 

Phosphoric acid is capable of existing in three different states or modifica- 
tions, forming three separate classes of salts which differ completely in pro- 
perties and constitution. They are distinguished by the names tribasic, 
bibasic, and monobasic acids, according to the number of equivalents of base 
required to form neutral salts. 

Tribasic or Common Phosphoric Acid. — "When commercial phosphate of soda 
is dissolved in water and the solution mixed with acetate of lead, an abundant 
white precipitate of phosphate of lead falls, which may be collected on a 
filter, and well washed. While still moist, this compound is suspended in 
distilled water, and an excess of sulphuretted hydrogen gas passed into it. 
The protoxide of lead is converted into sulphide, which subsides as a black 
insoluble precipitate, while phosphoric acid remains in solution, and is easily 
deprived of the residual sulphuretted hydrogen by a gentle heat. 

The soda-salt employed in this experiment contains the tribasic modifica- 
tion of phosphoric acid; of the three equivalents of base, two consist of soda 
and one of water ; when mixed with solution of lead, a tribasic phosphate of 
the oxide of that metal falls, which when decomposed by sulphuretted hydro- 
gen, yields sulphide of lead and a hydrate of the acid containing three 
equivalents of water in intimate combination. 

f 2 eq. soda — — 7 2 eq. acetate of soda. 

Phosphate J 1 „ water 7I ,, hydrated acetic acid. 

of soda 1 1 ,, phos-~l 

[_ phoric acid J 

acetic acid' 



3 eq. acetate J -1 



acetic acid 




of lead (3 „ oxide of lead ^ X ec l- tribasic Phosphate 

of lead. 



{3 eq. lead -? 3 eq. sulphide of lead. 
3 ,, oxygen 
1 „ phos- 1 
phoric acid j 
3 eq. sulphuretted J 3 eq. sulphur" 

hydrogen \3 „ hydrogen — — ^^ 1 eq. tribasic hydrate of 

phosphoric acid. 

The solution of tribasic hydrate may be concentrated hy evaporation in 
vacuo over sulphuric acid until it crystallizes in thin deliquescent piatos. 
The same compound in beautiful crystals, resembling those of sugar-candy, 
has been accidentally formed. 1 It undergoes no change by boiling with 
water, but when heated alone to 400° (204°-4C) loses some of its combined 
water, and becomes converted into a mixture of the bibasic and monobasic 
hydrates. At a red heat it becomes entirely changed to monohydrate, which, 
at a still higher temperature, sublimes. 

Tribasic phosphoric acid is characterized by the yellow insoluble salt it 
forms with protoxide of silver. 

* Peligot, Ann. Cliim. et I'hys. Ixxiii. 286. 



CHEMISTRY OP THE METALS. 213 

Bibasic Phosphoric Acid, or Pyrophosphoric Acid. — "When common phos- 
phate of soda, containing 

2NaO, HO, P0 5 +24HO, 
is gently heated, the 24 equivalents of water of crystallization are expelled, 
and the salt becomes anhydrous ; but if the heat be raised to a higher point, 
the basic water is also driven off, and the acid passes into the second or 
bibasic modification. M the altered salt be now dissolved in water, this new 
compound, the bibasic phosphate of soda, crystallizes out. When mixed with 
solution of acetate of lead, bibasic phosphate of lead is thrown down, which, 
decomposed by sulphuretted hydrogen, furnishes a solution of the bibasio 
hydrate. This solution may be preserved without change at common tem- 
peratures, but when heated, an equivalent of water is taken up, and the 
substance passes back again into the tribasic modification. 

Crystals of this hydrate have also been observed by M. Peligot. Their 
production was accidental. The bibasic phosphates soluble in water give a 
white precipitate with solution of silver. 

Monobasic, or Metaphosphoric Acid. — When common tribasic phosphate of 
soda is mixed with solution of tribasic hydrate of phosphoric acid, and ex- 
posed, after proper concentration, to a low temperature, prismatic crystals 
are obtained, which consist of a phosphate of soda having two equivalents of 
basic water. 

NaO, 2HO, P0 5 -f 2HO. 

When this salt is very strongly heated, both the water of crystallization 
and that contained in the base are expelled, and monobasic phosphate of 
soda remains. This may be dissolved in cold water, precipitated with ace- 
tate of lead, and the lead-salt, as before, decomposed by sulphuretted hy- 
drogen. 

The^solution of the monobasic hydrate is decomposed rapidly by heat, 
becoming converted into tribasic hydrate. It possesses the property of co- 
agulating albumen, which is not enjoyed by either of the preceding modifi- 
cations. Monobasic alkaline phosphates precipitate nitrate of silver white. 

The glacial phosphoric acid of pharmacy is, when pure, hydrate of mono- 
basic phosphoric acid : it contains HO, P0 5 . 

Anhydrous phosphoric acid, prepared by burning phosphorus in dry air, 
when thrown into water, forms a variable mixture of the three hydrates. 
When heated, a solution of the tribasic hydrate alone remains. 1 See also 
phosphates of soda. 

Binary Theory of Salts. — The great resemblance in properties between the 
two classes of saline compounds, the haloid and oxy-salts, has very naturally 
led to the supposition that both might possibly be alike constituted, and that 
the latter, instead of being considered compounds of an oxide and an acid, 
might with greater propriety be considered to contain a metal in union with 
a compound salt-radical, having the chemical relations of chlorine and 
iodine. 

On this supposition sulphate and nitrate of potassa will be constituted in 
the same manner as chloride of potassium, the compound radical replacing 
the simple one. 

Old view. New view. 

KO-fS0 3 K-fS0 4 

KO + N0 5 K-fN0 6 

1 The three modifications of phosphoric acid possess properties so dissimilar that they might 
really he considered three distinct, although intimately related bodies. It is exceedingly 
remarkable, that when their salts are subjected to electro-chemical decomposition, the acids 
travel unaltered, a tribasic salt giving at the positive electrode a solution of common phos- 
phoric acid; a bibasic salt, one of pyrophospboric acid ; and a monobasic salt, one of meta- 
phosphoric acid (Professor Daniell and Dr. Miller, Phil. Trans, for 1844, p. 1). 



214 CHEMISTRY OF THE METALS. 

Hydra ted sulphuric acid will be, like hydrochloric acid, a hydride of a salt- 
radical, 

H+S0 4 . 

When the latter acts upon metallic zinc, the hydrogen is simply displaced, 
and the metal substituted ; no decomposition of water is supposed to occur, 
and, consequently, the difficulty of the old hypothecs is at an end. When 
the acid is poured upon a metallic oxide, the same reaction occurs as in the 
case of hydrochloric acid, water and a haloid salt are produced. All acids 
must be, in fact, hydrogen acids, and all salts haloid salts, with either simple 
or compound radicals. 

This simple and beautiful theory is not by any means new ; it was sug- 
gested by Davy, who proposed to consider hydrogen as the acidifying prin- 
ciple in the common acids, and lately revived and very happily illustrated by 
Liebig. It is supported by a good deal of evidence derived from various 
sources, and has received great help from a series of exceedingly interesting 
experiments on the electrolysis of saline solutions, by the late Professor 
Daniell. 1 The necessity of creating a great number of non-insoluble com- 
pounds is often urged as an objection to the new view; but the same objec- 
tion applies to the old mode of considering the subject. Hyposulphurous 
acid and hyposulphuric acid are unknown in their free states. The com- 
pounds S 2 2 and S 2 4 are as hypothetical as the substances S 2 3 and S 2 6 . 
The same remark applies to almost every one of the organic acids ; and, what 
is well worthy of notice, those acids which, like sulphuric, phosphoric, and 
carbonic acids, may be obtained in a separate state, are destitute of all acid 
properties so long as the anhydrous condition is retained. 

Some very interesting observations have been published lately by M. Ger- 
hardt, 1 which are likely to hasten a change in the notation of acids generally. 

It has been pointed out that sulphvric and nitric acid, which, according 
to the theory of oxygen acids, are considered as compounds respectively of 
teroxide of sulphur and pentoxide of nitrogen with water, S0 3 ,HO, and N0 5 , 
HO, may be considered likewise as hydrogen acids, analogous to hydro- 
chloric and hydrocyanic acid. 

Hydrochloric acid HC1 

Hydrocyanic acid ; HC2N 

Sulphuric acid ) TTSO 



Hydrosulphanic acid 

Nitric acid 

Hydronitranic acid 



Nitric acid Y HN0 6 . 



Among the many facts which have been adduced in favour of the theory 
of oxygen acids, the preparation of the so-called anhydrous acids S0 3 and 
NO (see pages 124 and 135) has always been considered as powerful props. 
On the other hand, the followers of the theory of hydrogen acids have inva- 
riably called attention to the scarcity of the so-called anhydrous acids, and 
especially to the fact that, with a few exceptions, they are entirely. wanting 
in Organic Chemistry. The researches of M. Gerhardt just referred to, 
have furnished the means of making the anhydrous organic acids ; but the 
circumstances under which they are produced exhibit these substances in a 
perfectly new light, and prove that they stand in a very different relation to 
the hydrated acids from what is generall}' assumed. 

If dry benzoate of soda be heated with chloride of benzoyl (see page 399) 
to a temperature of 266° (130°C), a limpid liquid is formed, which is de- 

1 See Daniell's Introduction to Chemical Philosophy, 2d edition, p. 533. 
9 Chem. Soc. Quar. Jour. v. 127. 



CHEMISTRY OF THE METALS. 215 

composed with deposition of chloride of sodium when heated a few degrees 
higher ; there is formed, at the same time, a white crystalline product, 
which has exactly the composition of anhydrous benzoic acid, for it contains 
Ci 4 H 5 3 or BzO, if we represent C H H 5 2 by Bz. The decomposition which 
takes place is represented by the following equation : — 
BzO,NaO + BzCl=NaCl-f2BzO. 

The new substance crystallizes in beautiful oblique prisms, fusible at 90° -4 
(33°C), and volatile without decomposition. It is insoluble in water, but 
readily dissolves in alcohol and ether ; these solutions are perfectly neutral to 
test-paper. Cold water has not the slightest effect upon this body j by boil- 
ing water it is gradually converted into benzoic acid. This change immedi- 
ately occurs with boiling solutions of the alkalis. Boiling alcohol converts 
it into benzoate of etihyl. From the mode of formation, it is evident that 
the substance in question cannot be regarded as anhydrous benzoic acid, al- 
though it agrees with that substance in composition. It is obviously a sort 
of a salt, benzoate of benzoyl, or benzoic acid in which one equivalent of hy- 
drogen is replaced by benzoyl. 

Benzoic acid BzO, HO 

New compound BzO,BzO. 

If an additional support for this view was required, it would be found in 
the circumstance that chloride of benzoyl acts in exactly the same manner 
_ upon cumate, cinnamate, and salicylate of soda, a series of compounds be- 
ing produced which are perfectly analogous to the preceding substance, but 
contain in the place of benzoyl cuminyl, C 20 H 12 O 2 =Cm ; cinnamyl, Ci S H 7 2 = 
Ci; or s alky I, C 14 H 5 4 =S1. 

Benzoic acid BzO,HO 

Benzoate of benzoyl BzO, BzO 

Benzoate of cuminyl , BzO,CmO 

Benzoate of cinnamyl BzO,CiO 

Benzoate of salicyl BzO,S10. 

These substances are for the most part fusible, odourless solids, or oils 
heavier than water. With the alkalis they yield a mixture of the acids from 
which they have been produced. Several are not volatile without decompo- 
sition. 

A perfectly similar series of substances has been obtained with acetic acid. 
The acetic chloride, C1C 4 H 3 2 , corresponding to chloride of benzoyl, is formed 
in a most interesting process, namely, by the action of pentachloride of 
phosphorus (see page 168) upon acetate of soda, when chloride of sodium, 
oxichloride of phosphorus, PC1 3 2 , and chloride of acetetyl 1 are formed. 
NaO,C4H 3 3 -|-PCl 5 =NaCl+PCl 3 2 -fC 4 H 3 2 Cl. 

The action of chloride of acetetyl upon dry acetate of soda gives rise to 
the formation of an oily liquid, which has the composition of anhydrous 
acetic acid, C 4 H 3 3 , but which in reality is acetate of acetetyl — C 4 H..0 2 , 
4 H 3 O 2 ,O. 2 This liquid boils at 278°-6 (137°C) ; it is not miscible at once 

1 Acetetyl in order to distinguish it from acetyl, C4H3. 

3 This formula requires an equivalent of oxygen to produce two equivalents of anhydrous 
acetic acid. 

C-:H 3 02 ; C 4 H 3 020+0=2(C4H302,0). 
In the reaction "between acetate of soda and chloride of acetyle, an equivalent of oxygen from 
the soda converts the acetetyl into anhydrous acetic acid with the formation of chloride of 
sodium. 

NaO.C4H 3 O3+C4H 3 O2Cl=2(C 4 H303)+NaCl. 
Acetetyle here spoken of, is from its composition acetous or aldehydic acid. — It. B. 



216 CHEMISTRY OF THE METALS. 

with cold water, but only after continued agitation. Hot water dissolves it 
at once with formation of acetic acid. 

The application to inorganic compounds of the method, by means of which 
these substances are produced, promises in future very important materials 
for the elaboration of several of the most interesting questions with which 
chemists are engaged at the present moment. 

The general application of the binary theory still presents a few difficul- 
ties. But it is very probable that the progress of discovery will ultimately 
lead to its universal adoption, which would greatly simplify many parts of 
the science. One great inconvenience will be the change of nomenclature 
involved. 



CLASSIFICATION OF METALS. 
1. 

Metals of the Alkalis. 

Potassium, Lithium, 

Sodium, Ammonium.* 
2. 
dfetals of the Alkaline Earths. 

Barium, Calcium, 

Strontium, Magnesium. 
3. 
Metals of the Earths Proper. 

Aluminium, Norium, 

Beryllium, Thorium, 

Yttrium, Cerium, 

Erbium, Lantanum, 

Terbium, Didymium. 
Zirconium, 

4. 
Oxidalle Metals proper, whose Oxides form powerful Bases. 

Manganese, Zinc, 

»n Iron, Cadmium, 

Chromium, Bismuth, 

Nickel, Lead, 

Cobalt, Uranium. 
Copper, 

5. 
Oxidalle Metals Proper, whose Oxides form weak Bases, or Acids. 

Vanadium, Titanium, 

Tungsten, Tin, 

Molybdenum, Antimony, 

Tantalum, Arsenic, 

Niobium, Tellurium, 

Pelopium, Osmium. 
6. 
Metals Proper, whose Oxides are reduced by Heat ; Noble 3Ietals. 

Gold, Palladium, 

Mercury, Iridium, 

Silver, Ruthenium, 

Platinum, Rhodium. 

k This hypothetical substance is merely placed with the metals for the sake of convenience, 
us will be apparent in the sequel. 



POTASSIUM. 217 



SECTION I. 
METALS OF THE ALKALIS. 



POTASSIUM. 

Potassium was discovered by Sir H. Davy in 1807, who obtained it in 
very small quantity by exposing a piece of moistened hydrate of potassa to 
the action of a powerful voltaic battery, the alkali being placed between a 
pair of platinum plates put into connection with the apparatus. Processes 
have since been devised for obtaining this curious metal in almost any 
quantity that can be desired. 

An intimate mixture of carbonate of potassa and charcoal is prepared by 
calcining, in a covered iron pot, the crude tartar of commerce ; when cold, 
it is rubbed to powder, mixed with one-tenth part of charcoal in small lumps, 
and quickly transferred to a retort of stout hammered iron ; the latter may 
be one of the iron bottles in which mercury is imported, a short and some- 
what wide iron tube having been fitted to the aperture. The retort is placed 
upon its side, in a furnace so constructed that the flame of a very strong 
fire, fed with dry wood, may wrap round it, and maintain every part at an 
uniform degree of heat, approaching to whiteness. A copper receiver, 
divided in the centre by a diaphragm, is connected to the iron pipe, and kept 
cool by the application of ice, while the receiver itself is partly filled with 
naphtha or rock-oil, in which the potassium is to be preserved. Arrange- 
ments being thus completed, the fire is gradually raised until the requisite 
temperature is reached, when decomposition of the alkali by the charcoal 
commences, carbonic oxide gas is abundantly disengaged, and potassium 
distils over, and falls in large melted drops into the liquid. The pieces of 
charcoal are introduced for the purpose of absorbing the melted carbonate 
of potassa, and preventing its separation from the finely divided carbonaceous 
matter. 

If the potassium be wanted absolutely pure, it must be afterwards re-dis- 
tilled in an iron retort, into which some naphtha has been put, that its 
vapour may expel the air, and prevent the oxidation of the metal. 

Potassium is a brilliant white metal, with a high degree of lustre; at the 
common temperature of the air it is soft, and may be easily cut with a knife, 
but at 32° (0°C) it is brittle and crystalline. It melts completely at 136° 
(57°-77C), and distils at a low red heat. The density of this remarkable 
laetal is only 0-865, water being unity. 

Exposed to the air, potassium oxidizes instantly, a tarnish covering the 
surface of the metal, which quickly thickens to a crust of caustic potassa. 
Thrown upon water, it takes fire spontaneously, and burns with a beautiful 
purple flame, yielding an alkaline solution. When brought into contact with 
a little water in a jar standing over mercury, the liquid is decomposed with 
great energy, and hydrogen liberated. Potassium is always preserved under 
the surface of naphtha. 

The equivalent of potassium (kalium) is 39; and its symbol, K. 
19 



218 POTASSIUM. 

There are two compounds of this metal with oxygen, — potassa and teroxide 
of potassium. 

Potassa, Potash, or Protoxide of Potassium, KO, is produced when 
potassium is heated in dry air ; the metal burns, and becomes entirely con- 
verted into a volatile, fusible, white substance, which is anhydrous potassa. 
Moistened with water, it evolves great heat, and forms the hydrate. 

The hydrate of potassa, KO, HO, is a very important substance, and one 
of great practical utility. It is always prepared for use by decomposing the 
carbonate by hydrate of lime, as in the following process, which is very con- 
tenient : — 10 parts of carbonate of potassa are dissolved in 100 parts of 
water, and heated to ebullition in a clean untinned iron, or still better, silver 
vessel ; 8 parts of good quicklime are meanwhile slaked in a covered basin, 
and the resulting hydrate of lime added, little by little, to the boiling solu- 
tion of carbonate, with frequent stirring. When all the lime has been in- 
troduced, the mixture is suffered to boil a few minutes, and then removed 
from the fire, and covered up. In the course of a very short time, the solu- 
tion will have become quite clear, and fit for decantation, the carbonate of 
lime, with the excess of hydrate, settling down as a heavy, sandy precipi- 
tate. The solution should not effervesce with acids. 

It is essential in this process that the solution of carbonate of potassa be 
dilute, otherwise the decomposition becomes imperfect ; the proportion of 
lime recommended is much greater than that required by theory, but it is 
always proper to have an excess. 

The solution of hydrate, or, as it is commonly called, caustic potassa, may 
be concentrated by quick evaporation in the iron or silver vessel to any 
desired extent ; when heated until vapour of water ceases to be disengaged, 
and then suffered to cool, it furnishes the solid hydrate, containing single 
equivalents of potassa and water. 

Pure hydrate of potassa is a white solid substance, very deliquescent and 
soluble in water ; alcohol also dissolves it freely, which is the case with com- 
paratively few of the compounds of this base ; the solid hydrate of com- 
merce, which is very impure, may thus be purified. The solution of this 
substance possesses, in the very highest degree, the properties termed alka- 
line ; it restores the blue colour to litmus which has been reddened by an 
acid ; neutralizes completely the most powerful acids ; has a naseous and 
peculiar taste, and dissolves the skin, and many other organic matters, when 
the latter are subjected to its action. It is constantly used by surgeons as a 
cautery, being moulded into little sticks for that purpose. 

Hv Irate of potassa, both in the solid state and in solution, rapidly absorbs 
carbonic acid from the air ; hence it must be kept in closely stopped battles. 
"When imperfectly prepared, or partially altered by exposure, it efferraicei 
with an acid. 

The water in this compound cannot be displaced by heat, the hydrate vo- 
latilizing as a whole at a very high temperature. 

The following table of the densities and value in real alkali of different 
solutions of hydrate of potassa is given on the authority of Dr. Dalton. 



cnsity 

1-68 


1-G0 


1-52 


1-47 


1-44 


1-42 


2 -39 


1-36 



Percentage of 
real alkali. 



51-2 


1-33 


46-7 


1-28 


42-9 


1-23 


39-6 


1-19 


36-8 


115 


34-4 


111 


32-4 


1-06 


29-4 





r» - + „ Percentnin 

density, real alk. 

26-3 

23-4 

19-5 

16-2 

130 

9-5 

4-7 



POTASSIUM. 219 

Teroxide op potassium, K0 3 . — This is an orange-yellow fusible substance, 
generated when potassium is burned in excess of dry oxygen gas, and also 
formed, to a small extent, when hydrate of potassa is long exposed, in a 
melted state, to the air. When nitre is decomposed by a strong heat, per- 
oxide of potassium is also produced. It is decomposed by water into potassa, 
which unites with the latter, and into oxygen gas. 

Carbonate of potassa, KO, C0 2 -j-2HO. — Salts of potassa containing a 
vegetable acid are of constant occurrence in plants, where they perform im- 
portant, but not yet perfectly understood, functions in the economy of those 
beings. The potassa is derived from the soil, which, when capable of sup- 
porting vegetable life, always contains that substanee. When plants are 
burned, the organic acids are destroyed, and the potassa left in the state of 
carbonate. 

It is by these indirect means that carbonate, and, in fact, nearly all the 
salts of potassa, are obtained ; the great natural depository of the alkali is 
the felspar of granitic and other unstratified rocks, where it is combined 
with silica, and in an insoluble state. Its extraction thence is attended with 
too many difficulties to be attempted on the large scale; but when these 
rocks disintegrate into soils, and the alkali acquires solubility, it is gradually 
taken up by plants, and accumulates in their substance in a condition highly 
favourable to its subsequent applications. 

Potassa-salts are always most abundant in the green and tender parts of 
plants, as may be expected, since from these evaporation of nearly pure 
water takes place to a large extent ; the solid timber of forest trees contains 
comparatively little. 

In preparing the salt on an extensive scale, the ashes are subjected to a 
process called lixiviation ; they are put into a large cask or tun, having an 
aperture near the bottom, stopped by a plug, and a quantity of water is 
added. After some hours the liquid is drawn off, and more water added, 
that the whole of the soluble matter may be removed. The weakest solutions 
are poured upon fresh quantities of ash, in place of water. The solutions 
are then evaporated to dryness, and the residue calcined, to remove a little 
brown organic matter ; the product is the crude potash or pearlas'h of com- 
merce, of which very large quantities are obtained from Russia and America. 

This salt is very impure ; it contains silicate and sulphate of potassa, 
chloride of potassium, &c. 

The purified carbonate of potassa of pharmacy is prepared from the crude 
article, by adding an equal weight of cold water, agitating, and filtering ; 
most of the foreign salts are, from their inferior degree of solubility, left 
behind. The solution is then boiled clown to a very small bulk, and suffered 
to cool, when the carbonate separates in small crystals containing 2 equiv. 
of water, which are drained from the mother-liquor, and then dried in a stove. 

A still purer salt may be obtained by exposing to a red-heat purified 
cream of tartar (acid tartrate of potassa), and separating the carbonate by 
solution in water and crystallization, or evaporation to dryness. 

Carbonate of potassa is extremely deliquescent, and soluble in less than 
its own weight of water ; the solution is highly alkaline to test-paper. It is 
insoluble in alcohol. By heat the water of crystallization is driven off, and 
by a temperature of full ignition the salt is fused, but not otherwise changed. 
This substance is largely used in the arts, and is a compound of great im- 
portance. 

Bicarbonate of potassa, KO, C0 2 -{-HO, C0 2 . — When a stream of car- 
bonic acid gas is passed through a cold solution of carbonate of potassa, the 
gas is rapidly absorbed, and a white, crystalline, and less soluble substance 
separated, which is the new compound. It is collected, pressed, i e-dissolved 
in warm water, and the solution left to crystallize. 



220 POTASSIUM. 

Bicarbonate of potassa is much less soluble than simple carbonate ; it re- 
quires for that purpose 4 parts of cold water. The solution is nearly neutral 
to test-paper, and has a much milder taste than the preceding salt. When 
boiled, carbonic acid is disengaged. The crystals, which are large and beau- 
tiful, derive their form from a right rhombic prism ; they are decomposed 
by heat, water and carbonic acid being extricated, and simple carbonate left 
behind. 

Nitrate op potassa; nitre; saltpetre, KO, N0 5 . — This important 
compound is a natural product, being disengaged by a kind of efflorescence 
from the surface of the soil in certain dry and hot countries. It may also be 
produced by artificial means, namely, by the oxidation of ammonia in pres- 
ence of a powerful base. 

In France, large quantities of artificial nitre are prepared by mixing animal 
refuse of all kinds with o 1 "* mortar or hydrate of lime and earth, and placing 
the mixture in heaps, protected from the rain by a roof, but freely exposed 
to the air. From time to time the heaps are watered with putrid urine, and 
the mass turned over, to expose fresh surfaces to the air. When much salt 
has been formed, the mixture is lixiviated, and the solution, which contains 
nitrate of lime, mixed with carbonate of potassa ; carbonate of lime is formed, 
and the nitric acid transferred to the alkali. The filtered solution is then 
made to crystallize, and the crystals purified by re-solution and crystalliza- 
tion several times repeated. 

All the nitre used in this country comes from the East Indies ; it is dis- 
solved in water, a little carbonate of potassa added to precipitate lime, and 
then the salt purified as above. 

Nitrate of potassa crystallizes in anhydrous six-sided prisms, with dihedral 
summits; it is soluble in 7 parts of water at 60° (15°-5C), and in its own 
weight of boiling water. Its taste is saline and cooling, and it is without 
action on vegetable colours. At a temperature below redness it melts, and 
by a strong heat is completely decomposed. 

When thrown on the surface of many metals in a state of fusion, or when 
mixed with combustible matter and heated, rapid oxidation ensues, at the 
expense of the oxygen of the nitric acid. Examples of such mixtures are 
found in common gunpowder, and in nearly all pyrotechnic compositions, 
which burn in this manner independently of the oxygen of the air, and even 
under water. Gunpowder is made by very intimately mixing together nitrate 
of potassa, charcoal, and sulphur, in proportions which approach 1 eq. nitre, 
3 eq. carbon, and 1 eq. sulphur. 

These quantities give, reckoned to 100 parts, and compared with the pro- 
portions used in the manufacture of the English government powder, 1 the 
following results : — 

Theory. Proportions in practice. 

Nitrate of potassa 74-8 75 

Charcoal 13-3 15 

Sulphur 11-9 10 

100- 100 

The nitre is rendered very pure by the means already mentioned, freed 
from water by fusion, and ground to fine powder : the sulphur and charcoal, 
the latter being made from light wood, as dogwood or elder, are also finely 
ground, after which the materials arc weighed out, moistened with water, 
and thoroughly mixed, by grinding under an edge-mill. The mass is then 
subjected to great pressure, and the mill-cake thus produced broken in pieces, 

1 Dr. M'Culloch, Ency. Brit. 



POTASSIUM. 221 

and placed in sieves made of perforated vellum, moved by machinery, each 
containing, in addition, a round piece of heavy wood. The grains of powder 
broken off by attrition fall through the holes in the skin, and are easily sepa- 
rated from the dust by sifting. The powder is, lastly, dried by exposure to 
steam-heat, and sometimes glazed or polished by agitation in a kind of cask 
mounted on an axis. 

When gunpowder is fired, the oxygen of the nitrate of potassa is trans 
ferred to the carbon, forming carbonic acid ; the sulphur combines with the 
potassium, and the nitrogen is set free. The large volume of gas thus pro- 
duced, and still farther expanded by the very exalted temperature, suffi- 
ciently accounts for the explosive effects. 

Sulphate of potassa, KO,S0 3 . — The acid residue left in the retort when 
nitric acid is prepared is dissolved in water, and neutralized with crude car- 
bonate of potassa. The solution furnishes, on cooling, hard transparent 
crystals of the neutral sulphate, which may be re-dissolved in boiling water, 
and re-crystallized. 

Sulphate of potassa is soluble in about 10 parts of cold, and in a much 
smaller quantity of boiling water ; it has a bitter taste, and is neutral to 
test-paper. The crystals much resemble those of quartz in figure and ap 
pearance ; they are anhydrous, and decrepitate when suddenly heated, 
which is often the case with salts containing no water of crystallization. 
They are quite insoluble in alcohol. 

Bisulphate of potassa, KO,S0 3 -{- HO,S0 3 . The neutral sulphate in 
powder is mixed with half its weight of oil of vitriol, and the whole evapo- 
rated quite to dryness in a platinum vessel, placed under a chimney ; the 
fused salt is dissolved in hot water, and left to crystallize. The crystals 
have the figure of flattened rhombic prisms, and are much more soluble than 
the neutral salt, requiring only twice their weight of water at 60° (15°-5C), 
and less than half that quantity at 212° (100°C). The solution has a sour 
taste and strong acid reaction. 

Bisulphate of potassa, anhydrous, KO,2S0 3 . — Equal weights of neutral 
sulphate of potassa and oil of vitriol are dissolved in a small quantity of 
warm distilled water, and set aside to cool. The anhydrous sulphate crys- 
tallizes out in long delicate needles, which if left several days in the mother- 
liquor disappear, and give place to crystals of the ordinary hydrated bisul- 
phate above described. This salt is decomposed by a large quantity of 
water. 1 

Sesquisulphate of potassa, 2(KO,S0 3 ) -f- HO,S0 3 . — A salt, crytallizing 
in fine needles resembling those of asbestos, and having the composition 
stated, was obtained by Mr. Phillips from the nitric acid residue. M. Jacque- 
lain was unsuccessful in his attempts to reproduce this compound. 

Chlorate of potassa, KO,C10 5 . — The theory of the production of chloric 
acid, by the action of chlorine gas on a solution of caustic potassa, has been 
already described (p. 145). 

Chlorine gas is conducted by a wide tube into a strong and warm solution 
of carbonate of potassa, until absorption of the gas ceases. The liquid is, 
if necessary, evaporated, and then allowed to cool, in order that the slightly 
soluble chlorate may crystallize out. The mother-liquid affords a second 
crop of crystals, but they are much more contaminated by chloride of potas • 
sium. It may be purified by one or two re-crystallizations. 

Chlorate of potassa is soluble in about 20 parts of cold, and 2 of boiling 
water; the crystals are anhydrous, flat, and tabular; in taste it somewhat, 
resembles nitre. Heated, it disengages oxygen gas from both acid and base, 
and leaves chloride of potassium, By arresting the decomposition when the 

* Jarnnolain, Ann. Chim. et Phy?. vol. vii. p. 311 
19* 



222 POTASSIUM. 

evolution of gas begins, and re-dissolving the salt, perchlorate of potassa 
and chloride of potassium may be obtained. 

This salt deflagrates violently with combustible matter, explosion often 
occurring by friction or blows. When about one grain weight of chlorate 
and an equal quantity of sulphur are rubbed in a mortar, the mixture ex- 
plodes with a loud report ; hence it cannot be used in the preparation of gun- 
j)owder instead of nitrate of potassa. Chlorate of potassa is now a large 
article of commerce, being employed, together with phosphorus, in making 
instantaneous light matches. 

Perchlorate or potassa, KO,C10 7 . — This has been already noticed 
under the head of perchloric acid. It is best prepared by projecting 
powdered chlorate of potassa into warm nitric acid, when the chloric acid is 
resolved into perchloric acid, chlorine, and oxygen gases. The salt is 
separated by crystallization from the nitrate. Perchlorate of potassa is a 
very feebly soluble salt ; it requires 55 parts of cold water, but is more freely 
taken up at a boiling heat. The crystals are small, and have the figure of 
an octahedron, with square base. It is decomposed by heat, in the same 
manner as chlorate of potassa. 

Sulphides of potassium. — There are not less than five or six distinct 
compounds of potassium and sulphur, of which, however, only three are of 
sufficient importance to be noticed here ; these are the compounds, contain- 
ing KS, KS 3 , and KS 5 . 

Simple or protosulphide of potassium, is formed by directly combining the 
metal with sulphur, or by reducing sulphate of potassa at a red-heat by hy- 
drogen or charcoal powder. Another method is to take a strong solution of 
hydrate of potassa, and after dividing it into two equal portions, saturate 
the one with sulphuretted hydrogen gas, and then add the remainder. The 
whole is then evaporated to dryness in a retort, and the residue fused. 

The protosulphide is a crystalline cinnabar-red mass, very soluble in water. 
The solution has an exceedingly offensive and caustic taste, and is decom- 
posed by acids, even carbonic acid, with evolution of sulphuretted hydrogen, 
and formation of a salt of the acid used. This compound is a strong sulphur- 
base, and unites with the sulphides of hydrogen, carbon, arsenic, &c., forming 
crystallizable saline compounds, One of these, KS-f-HS, is produced when 
hydrate of potassa is saturated with sulphuretted hydrogen, as before men- 
tioned. 

The higher sulphides are obtained by fusing the protosulphide with dif- 
ferent proportions of sulphur. They are soluble in water, and decomposed 
by acids, in the same manner as the foregoing compound, with this addition, 
that the excess of sulphur is precipitated as a fine white powder. 

Hepar sulphuris is a name given to a brownish substance, sometimes used 
in medicine, made by fusing together different proportions of carbonate of 
potassa and sulphur. It is a variable mixture of the two higher sulphides 
with hyposulphite and sulphate of potassa. 

"When equal parts of sulphur and dry carbonate of potassa are melted to- 
gether at a temperature not exceeding 482° (250°C), the decomposition of 
the salt is quite complete, and all the carbonic acid is expelled. The fused 
mass dissolves in water, with the exception of a little mechanically-mixed 
sulphur, with dark brown colour, and the solution is found to contain nothing 
besides pentasulphide of potassium and hyposulphite of potassa. 

2 eq. potassium__ _^2 eq. of pentasulphide of po- 

eq. potassa \ 2 eq. oxygen^ ^^ sium. 

eq. potassa. 



{! 

, 9 , , / 10 eq. sulphur^^""""-^-^^^ 

I- eq. sulphur j 2 ^ su]phur Ir^^ l eq , hyposulphite of po- 




tassa. 



POTASSIUM. 



223 



When the mixture has been exposed to a temperature approaching that 
of ignition, it is found on the contrary to contain sulphate of potassa, arising 
from the decomposition of the hyposulphite which then occurs. 



4 eq. hyposul- 
phite of po- 
tassa 



1 eq. pentasulphide 
of potassium. 



4 eq. 
potassa 

4 eq. hy- 
posulph. 
acid 



1 eq. potassium 
1 eq. oxygen 
3 eq. potassa 
5 eq. sulphur 
3 eq. sulphur 
8 eq. oxygen 




3 eq. sulphate of 
potassa. 

From both these mixtures the pentasulphide of potassium may be ex- 
tracted by alcohol, in which it dissolves. 

When the carbonate is fused with half its weight of sulphur only, then the 
tersulphide, KS 3 , is produced instead of that above indicated ; 3 eq. of po- 
tassa and 8 eq. of sulphur containing the elements of 2 eq. sulphide and 1 
eq. hyposulphite. 

The effects described happen in the same manner when hydrate of potassa 
is substituted for the carbonate ; and also, when a solution of the hydrate is 
boiled with sulphur, a mixture of sulphide and hyposulphite always results. 

Chloride of potassium, KC1. — This salt is obtained in large quantity in 
the manufacture of chlorate of potassa ; it is easily purified from any portions 
of the latter by exposure to a dull red-heat. It is also contained in kelp, 
and is separated for the use of the alum-maker. 

Chloride of potassium closely resembles common salt in appearance, as- 
suming, like that substance, the cubic form of crystallization. The crystals 
dissolve in three parts of cold, and in a much less quantity of boiling water ; 
they are anhydrous, have a simple saline taste, with slight bitterness, and 
fuse when exposed to a red-heat. Chloride of potassium is volatilized by a 
very high temperature. 

Iodide of potassium, KI. — There are two different methods of preparing 
this important medicinal compound. 

(1.) When iodine is added to a strong solution of caustic potassa free from 
carbonate, it is dissolved in large quantity, forming a colourless solution 
containing iodide of potassium and iodate of potassa ; the reaction is the 
same as in the analogous case with chlorine. When the solution begins to 
be permanently coloured by the iodine, it is evaporated to dryness, and cau- 
tiously heated red-hot, by which the iodate of potassa is entirely converted 
into iodide of potassium. The mass is then dissolved in water, and after fil- 
tration, made to crystallize. 

(2.) Iodine, water, and iron-filings or scraps of zinc, are placed in a warm 
situation until the combination is complete, and the solution colourless. The 
resulting iodide of iron or zinc is then filtered, and exactly decomposed with 
solution of pure carbonate of potassa, great care being taken to avoid excess 
of the latter. Iodide of potassium and carbonate of protoxide of iron, or 
zinc, are obtained ; the former is separated by filtration, and evaporated 
until the solution is sufficiently concentrated to crystallize on cooling, the 
washings of the filter being added to avoid loss. 

Iodine _, Iodide of potassium. 

Iron 



Iodide of iron 



Carbonate of potassa 



{^ , f Potassium 

Potassa | Qxy 
Carbonic acid 




Carbonate of protoxide 
of iron. 



The second method is, on the whole, to be preferred. 



224 SODIUM. 

Iodide of potassium crystallizes in cubes, which are often, from some un- 
explained cause, milk-white and opaque ; they are anhydrous, and fuse 
readily when heated. The salt is very soluble in water, but not deliquescent, 
when pure, in a moderately dry atmosphere ; it is dissolved by alcohol. 

Solution of iodide of potassium, like those of all the soluble iodides, dis- 
solves a large quantity of free iodine, forming a deep brown liquid, not de- 
composed by water. 

Bromide of potassium, KBr. — This compound may be obtained by pro- 
cesses exactly similar to those just described, substituting bromine for the 
iodine. It is a colourless and very soluble salt, quite indistinguishable in 
appearance and general characters from the iodide. 



The salts of potassa are colourless, when not associated with a coloured 
metallic oxide or acid. They are all more or less soluble in water, and may 
be distinguished by the following characters : — 

(1.) Solution of tartaric acid added to a moderately strong solution of a 
potassa-salt, gives, after some time, a white, crystalline precipitate of cream 
of tartar ; the effect is greatly promoted by strong agitation. 

(2.) Solution of bichloride of platinum, with a little hydrochloric acid, if 
necessary, gives, under similar circumstances, a crystalline yellow precipi- 
tate, which is a double salt of bichloride of platinum and chloride of potas- 
sium. Both this compound and cream of tartar are, however, soluble in 
about 60 parts of cold water. An addition of alcohol increases the delicacy 
of both tests. 

(3.) Perchloric acid, and hydrofluosilicic acid, give rise to slightly-soluble 
white precipitates when added to a potassa-salt. 

(4.) Salts of potassa usually colour the outer blowpipe flame purple or 
violet ; this reaction is clearly perceptible only when the potassa-salts are 
pure. 

SODIUM. 

This metal was obtained by Davy very shortly after the discovery of po- 
tassium, and by similar means. It may be prepared in large quantity by 
decomposing carbonate of soda by charcoal at a high temperature. 

Six parts of anhydrous carbonate of soda are dissolved in a little hot 
water, and mixed with two parts of finely-powdered charcoal and one part 
of charcoal in lumps. The whole is then evaporated to dryness, transferred 
to the iron retort before described, and heated in the same manner to white- 
ness. A receiver containing rock-oil is adapted to the tube, and the whole 
operation carried on in the same way as when potassium is made. The pro- 
cess, when well conducted, is easier and more certain than that of making 
potassium. 

Sodium is a silver-white metal, greatly resembling potassium in every re- 
spect; it is soft at common temperatures, melts at 194° (90°C), and oxidizes 
very rapidly in the air. Its specific gravity is 0-972. Placed upon the sur- 
face of cold water, sodium decomposes that liquid with great violence, but 
seldom takes fire unless the motions of the fragment be restrained, and its 
rapid cooling diminished, by adding gum or starch to the water. With hot 
water it takes fire at once, burning with a bright yellow flame, and giving 
rise to a solution of soda. 

The equivalent of sodium is 23, and its symbol (Natrium) Na. 

Thei-e are two well-defined compounds of sodium and oxygen; the pro- 
toxide, anhydrous soda, NaO, and the binoxide, Na0 2 , or perhaps, teroxide 
Na0 3 ; they are framed by burning sodium in air or oxygen gas, and resem- 
ble in every respect the corresponding compounds of potassium. 

Hydrate of soda, NaO, HO. — This substance is prepared in practice by 



SODIUM 



225 



decomposing a some/what dilute solution of carbonate of soda "by hydrate of 
lime ; the description of the process employed in the case of hydrate of po- 
tassa, and the precautions necessary, apply word for word to that of soda. 

The solid hydi-ate is a white, fusible substance, very similar in properties 
to hydrate of potassa. It is deliquescent, but dries up again after a time in 
consequence of the absorption of carbonic acid. The solution is highly al- 
kaline, and a powerful solvent for animal matter ; it is used in large quan- 
tity for making soap. 

The strength of a solution of caustic soda may be roughly determined 
from a knowledge of its density, by the aid of the following table drawn up 
by Dr. Dalton. 



TABLE OF DENSITY. 



Percentage of 
real soda. 



77-8 


1-40 


63-6 


1-36 


53-8 


1-32 


46-6 


1-29 


41-2 


1-23 


36-8 


1-18 


34-0 


1-12 


31-0 


1-06 



Density. 



Percentage of 
real soda. 

.... 29-0 

.... 26-0 

.... 23-0 

.... 19-0 

.... 16-0 

.... 13-0 

.... 9-0 

.... 4-7 



Density. 

2-00 

1-85 

1-72 

1-63 

1-55 

1-50 

1-47 

1-44 

Carbonate op soda, NaO,CO 2 -}-10HO. — Carbonate of soda was once ex- 
clusively obtained from the ashes of sea-Aveeds, and of plants, such as the 
Salsola soda, which grew by the sea-side, or, being cultivated in suitable lo- 
calities for the purpose, were afterwards subjected to incineration. The 
barilla, yet employed to a small extent in soap-making, is thus produced in 
several places on the coast of Spain, as Alicant, Carthagena, &c. That 
made in Brittany is called varec. 

Carbonate of soda is now manufactured on a stupendous scale from com- 
mon salt, or rather from sulphate of soda, by a process of which the follow- 
ing is an outline : — 

A charge of 6001b. of common salt 1 is placed upon the hearth of a well- 
heated reverberatory furnace, and an equal weight of sulphuric acid of sp. 
gr. 1-6 poured upon it through an opening in the roof, and thoroughly min- 
gled with the salt ; hydrochloric acid gas is disengaged, which is either 
allowed to escape by the chimney, or condensed by suitable apparatus, and 
the salt is converted into sulphate of soda. This part of the process takes 
for completion about four hours, and requires much care and skill. 

The sulphate is next reduced to powder, and mixed with an equal weight 
of chalk or limestone, and half as much small coal, both ground or crushed. 
The mixture is thrown into a reverberatory furnace, and heated to fusion, 
with constant stirring ; 2 cwt. is about the quantity operated on at once. 
When the decomposition is judged complete, the melted matter is raked from 
the surface into an iron trough, where it is allowed to cool. When cold, it 
is broken up into little pieces, and lixiviated with cold or tepid water. The 
solution is evaporated to dryness, and the salt calcined with a little saw-dust 
in a suitable furnace. The product is the soda-ash, or British alkali of com- 
merce, which, when of good quality, contains from 48 to 52 per cent, of 
pure soda, partly in the state of carbonate, and partly as hydrate, the re- 
mainder being chiefly sulphate of soda and common salt, with occasional 
traces of sulphite or hyposulphite, and also cyanide of sodium. By dissolving 



1 Graham, Elements, p. 



226 sodium. 

soda-ash in hot water, filtering the solution, and then allowing it to cool 
slowly, the carbonate is deposited in large transparent crystals. 

The reaction which takes place in the calcination of the sulphate with 
chalk and coal-dust seems to consist, first, in the conversion of the sulphate 
of soda into sulphide of sodium by the aid of the combustible matter, and, 
secondly, in the double interchange of elements between that substance and 
the carbonate of lime. 



Sulphur Sulphide of calcium. 



Sulphide of sodium j |™J 



fLime^ 




Carbonate of lime -j \ Oxygen 

(Carbonic acid ""^^ Carbonate of soda. 

The sulphide of calcium combines with another proportion of lime to form 
a peculiar compound, which is insoluble in cold or slightly warm water. 

Other processes have been proposed, and even carried into execution, but 
the above, which was originally proposed by M. Leblanc, is found most ad- 
vantageous. 

The ordinary crystals of carbonate of soda contain ten equivalents of water, 
but by particular management the same salt may be had with fifteen, nine, 
seven, equivalents, or sometimes with only one. The common form of the 
crystal is derived from an oblique rhombic prism ; they effloresce in dry air, 
and crumble to a white powder. Heated, they fuse in their water of crys- 
tallization ; when the latter has been expelled, and the dry salt exposed to 
a full red-heat, it melts without undergoing change. The common crystals 
dissolve in two parts of cold, and in less than their own weight of boiling 
water ; the solution has a strong, disagreeable, alkaline taste, and a power- 
ful alkaline reaction. 

Bicarbonate of soda, NaO,C0 2 -f- HO,C0 2 . — This salt is prepared by 
passing carbonic acid gas into a cold solution of the neutral carbonate, or 
by placing the crystals in an atmosphere of the gas, which is rapidly ab- 
sorbed, while the crystals lose the greater part of their water, and pass into 
the new compound. 

Bicarbonate of soda, prepared by either process, is a crystalline white 
powder, which cannot be re-dissolved in warm water without partial decom- 
position. It requires 10 parts of water at 60° (15°-5C) for solution; the 
liquid is feebly alkaline to test-paper, and has a much milder taste than that 
of the simple carbonate. It does not precipitate a solution of magnesia. 
By exposure to heat, the salt is converted into neutral carbonate. 

A sesquicarbonate of soda containing 2NaO,3C0 2 -f-4HO has been described 
by Mr. Phillips ; like the sesquicarbonate of potassa, it is formed at plea- 
sure only with difficulty. This salt occurs native on the banks of the soda- 
lakes of Sokena in Africa, whence it is exported under the name of trona. 

Alkalimetry; Analysis of Hydrates and Carbonates of the Alkalis. — The 
general principle of these operations consists in ascertaining the quantity 
of real alkali in a given weight of the substance examined, by finding how 
much of the latter is required to neutralize a known quantity of an acid, as 
sulphuric acid. 

The first step is the preparation of a stock of dilute sulphuric acid of 
determinate strength ; containing, for example, 100 grains of real acid in 
every 1,000 grain-measures of liquid : ' a large quantity, as a gallon or more, 

1 The capacity of 1.000 grains of distilled water at 60° (15°5C). The grain-measure of water 
la often found a very convenient and useful unit of volume in chemical researches. Vessels 
graduated on this plan hear simple comparison with the imperial gallon and pint, and fre- 
quently also enable the operator to measure out a liquid of known density instead of weigh- 
ing it. 



sodium. 227 

may be prepared at once by the following means. The oil of vitriol is first 
examined; if it be good and of the sp. gr. 1-85 or near it, the process is ex- 
tremely simple ; every 49 grains of the liquid acid contains 40 grains of 
absolute acid ; the quantity of the latter required in the gallon, or 70,000 
grain-measures of dilute acid, will be of course 7,000 grains. This is equi 
valent to 8,571 grains of the oil of vitriol, for 

Real acid. Oil of vitriol. 

40 : 49 = 7000 : 8575 

All that is required to be done, therefore, is to weigh out 8,575 grains of 
oil of vitriol, and dilute it with so much water, that the mixture, when cold, 
shall measure exactly one gallon. 

It very often happens, however, that the oil of vitriol to be used is not so 
strong as that above mentioned ; in which case it is necessary to discover its 
real strength, as estimated from its saturating power. Pure anhydrous car- 
bonate of soda is prepared by heating to dull redness, without fusion, the 
bicarbonate ; of this salt 53 grains, or 1 eq., correspond to 31 grains of soda, 
and neutralize 40 grains of real sulphuric acid. 

A convenient quantity is carefully weighed out, and added, little by little, 
to a known weight, say 100 grains, of the oil of vitriol to be tried, diluted 
with four or five times its weight of water, until the liquid, after warming, 
becomes quite neutral to test-paper. By weighing again the residue of the 
carbonate, it is at once known how much of the latter has been employed ; 
the amount of real acid in the hundred parts of the oil of vitriol is then 
easily calculated. Thus, suppose the quantity of carbonate of soda used to 
be 105 grains ; then, 

Carb. soda. Sulpb. acid. 

53 : 40 = 105 : 79-24; 

79-24 grains of real acid are consequently contained in 100 grains Fig. 145 



of oil of vitriol ; consequently, 

79-24 : 100 = 7000 : 8833-82 



«R 



the weight in grains of the oil of vitriol required to make one 
gallon of the dilute acid. 

The " alkalimeter" is next to be constructed. This is merely a 
1000-grain measure, made of a piece of even, cylindrical glass tube, 
about 15 inches long and 0-6 inch internal diameter, closed at one 
extremity, and moulded into a spout or lip at the other. Fig. 146. 
A strip of paper is pasted on the tube and suffered to dry, after 
which the instrument is graduated by counterpoising it in a nearly 
upright position in the pan of a balance of moderate delicacy, and 
weighing into it, in succession, 100, 200, 300, &c, grains of dis- 
tilled water at 60° (15° -5C), until the whole quantity, amounting 
to 1,000 grains, has been introduced, the level of the water in the j 
tube being, after each addition, carefully marked with a pen upon J 
the strip of paper, while the tube is held quite upright, and the 
mark made between the top and the bottom of the curve formed by 
the surface of the water. The smaller divisions of the scale, of 10 
grains each, may then be made by dividing by compasses each of 
the spaces into ten equal parts. When the graduation is complete, 
and the operator is satisfied with its accuracy, the marks may be 
transferred to the tube itself by a sharp file, and the paper removed 
by a little warm water. The numbers are scratched on the glass with the 
hard end of the same file, or with a diamond. "When this alkalimeter is used 



2*28 s o d i u m . 

■with the dilute acid described, every division of the glass will correspond to 
one grain of real sulphuric acid. 

Let it be required, by way of example, to test the commercial value of 
soda-ash, or to examine it for scientific purposes : 50 grains of the sample 
are weighed out, dissolved in a little warm water, and, if necessary, the 
solution filtered ; the alkalimeter is then filled to the top of the scale with 
the test-acid, and the latter poured from it into the alkaline solution, which 
is tried from time to time with red litmus-paper. The addition of acid must 
of course be made very cautiously as neutralization advances. When the 
solution, after being heated a few minutes, no longer affects either blue or 
red test-paper, the measure of liquid employed is read off, and the quantity 
of soda present in the state of carbonate or hydrate in the 50 grains of salt 
found by the rule of proportion. Suppose 33 measures, consequently 33 
grains of acid, have been taken ; then 
Sulph. acid. Soda. 

40 : 31 = 33 : 25-57; 

the sample contains, therefore, 51-2 per cent, of available alkali. 

It will be easily seen that the principle of the process described admits of 
very wide application, and that, by the aid of the alkalimeter and carefully 
prepared test-acid, the hydrates and carbonates of potassa, soda, and am- 
monia, both in the solid state and in solution, can be examined with great 
ease aud accuracy. The quantity of real alkali in a solution of caustic am- 
monia may thus be determined, the equivalent of that substance, and the 
amount of acid required to neutralize a known weight, being inserted as the 
second and third terms in the above rule-of-three statement. The same acid 
answers for all. 

It is often desirable, in the analysis of carbonates, to determine directly 
the proportion of carbonic acid ; the following methods leave nothing to be 
desired in point of precision : — 

A small light glass flask (fig. 147) of three or four 
Fig. 117. ounces capacity, with lipped edge, is chosen, and a cork 

fitted to it. A piece of tube about three inches long is 
* ~ drawn out at one extremity, and fitted by means of a 

small cork and a bit of bent tube, to the cork of the 
flask. This tube is filled with fragments of chloride of 
calcium, prevented from escaping by a little cotton at 
either end; the joints are secured by sealing-wax. A 
short tube, closed at one extremity, and small enough to 
go into the flask, is also provided, and the apparatus is 
complete. Fifty grains of the carbonate to be examined 
are carefully weighed out and introduced into the flr.sk, 
together with a little water, the small tube is then filled with oil of vitriol, 
and placed in the flask in a nearly upright position, and leaning against its 
side in such a manner that the acid does not escape. The cork and chloride 
of calcium tube are then adjusted, and the whole apparatus accurately 
counterpoised on the balance. This done, the flask is slightly inclined, so 
that the oil of vitriol may slowly mix with the other substances and 
decompose the carbonate, the gas from which escapes in a dry state from 
the extremity of the tube. When the action has entirely ceased the liquid 
is heated until it boils, and the steam begins to condense in the drying-tube ; 
it is then left to cool, and weighed, when the loss indicates the quantity of 
carbonic acid. The acid must be in excess after the experiment. When 
carbonate of lime is thus analyzed, strong hydrochloric acid must be substi- 
tuted for the oil of vitriol. 

Instead of the above apparatus, a neat arrangement may be used which 




S O D I U M . 



229 



Fig. 148. 




was first suggested by Will and Fresenius. It consists of two small glass 
flasks, A and B, fig. 148, the latter being somewhat smaller than the former. 
Both the flasks are provided with a doubly perforated cork. A tube, open at 
both ends, but closed at the upper extremity by means of a small quantity of 
wax, passes through the cork of A, to the very 
bottom of the flask, whilst a second tube reach- 
ing to the bottom of B, establishes a communi- 
cation between the two flasks. The cork of B 
is provided, moreover, with a short tube, d. In 
order to analyse a carbonate, a suitable quan- 
tity (fifty grains) is put into A, together with 
some water. B is half filled with concentrated 
sulphuric acid, the apparatus tightly fitted and 
weighed. A small quantity of air is now 
sucked out of flask B by means of the tube d, 
whereby the air in A is likewise rarified. Im- 
mediately a portion of sulphuric acid ascends 
in the tube c, and flows over into flask A, 
causing a disengagement of carbonic acid, 
which escapes at d, after having been perfectly 
dried by passing through the bottle B. This 
operation is repeated until the whole of the carbonate is decomposed, and 
the process terminated by opening the wax stopper and drawing a quantity 
of air through the apparatus. The apparatus is now re-weighed. The dif- 
ference of the two weighings expresses the quantity of carbonic acid in the 
compound analysed. 1 

Sulphate of soda, Glauber's salts, NaO, S0 3 -4-10HO. — This is a by- 
product in several chemical operations ; it may of course be prepared 
directly, if wanted pure, by adding dilute sulphuric acid to saturation to a 
solution of carbonate of soda. It crystallizes in a figure derived from an 
oblique rhombic prism ; the crystals contain 10 eq. of water, are efllores- 
cent, and undergo watery fusion when heated, like those of the carbonate ; 
they are soluble in twice their weight of cold water, and rapidly increase in 
solubility as the temperature of the liquid rises to 91°-5 (33°C), when a 
maximum is reached, 100 parts of water dissolving 322 parts of the salt. 
Heated beyond this point, the solubility diminishes, and a portion of sul- 
phate is deposited. A warm saturated solution, evaporated at a high tempe- 
rature, deposits opaque prismatic crystals, which are anhydrous. This salt 
has a sbghtly bitter taste, and is purgative. Mineral springs sometimes con- 
tain it, as at Cheltenham. 

Bisulphate of soda, NaO,S0 3 -f- HO,S0 3 -J- 3HO. — This is prepared by 
adding to 10 parts of anhydrous neutral sulphate, 7 of oil of vitriol, evapo- 
rating the whole to dryness, and gently igniting. The bisulphate is very 
soluble in water, and has an acid reaction. It is not deliquescent. When 
very strongly heated, the fused salt gives up anhydrous sulphuric acid, and 
becomes simple sulphate ; a change which necessarily supposes the previous 
formation of a true anhydrous bisulphate, NaO,2S0 3 . 

Hyposulphite of soda, NaO, S 2 2 . — There are several modes of procu- 
ring this salt, which is now used in considerable quantity for jxhotographic 
purposes. One of the best is to form neutral sulphite of soda, by passing a 
stream of well washed sulphurous acid gas into a strong solution of carbo- 
nate of soda, and then to digest the solution with sulphur at a gentle heat 
during several days. By careful evaporation at a modern temperature, the 
Bait is obtained in large and regular crystals, which are very soluble in water. 

1 A conTenient mortification of this has been made by Dr. Yfetherill, (Jo urn. Frank. Inst.); 
and another by SchafTner. (Chem. Gazette, Jan. 15. 1S53.— R. B.) . 
20 



230 SODIUM. 

Nitrate of soda; cubic nitre, NaO, N0 5 . — Nitrate of soda occurs native, 
and in enormous quantity, at Atacama, in Peru, "where it forms a regular 
bed, of great extent, covered with clay and alluvial matter. The pure stilt 
commonly crystallizes in rhombohedrons, resembling those of calcareous 
spar, but is probably dimorphous. It is deliquescent, and very soluble in 
■water. Nitrate of soda is employed for making nitric acid, but cannot be 
used for gunpowder, as the mixture burns too slowly, and becomes damp in. 
the air. It has been lately used with some success in agriculture as a su- 
perficial manure or top-dressing. 

Phosphates of soda; common tribasic phosphate, 2NaO, HO, P0 5 -f 24 
HO. — This beautiful salt is prepared by precipitating the acid phosphate of 
lime obtained by decomposing bone-earth by sulphuric acid, with a slight 
excess of carbonate of soda. It crystallizes in oblique rhombic prisms, 
which are efflorescent. The crj^stals dissolve in 4 parts of cold water, and 
undergo the aqueous fusion when heated. The salt is bitter and purgative ; 
its solution is alkaline to test-paper. Crystals containing 14 equivalents of 
water, and having a form different from that above mentioned, have been 
obtained. 

A second tribasic phosphate, sometimes called subphosphate, 3NaO, 
P0 5 -f-24HO, is obtained by adding a solution of caustic soda to the prece- 
ding salt. The crystals are slender six-sided prisms, soluble in 5 parts of 
cold water. It is decomposed by acids, even carbonic, but suffers no change 
by heat, except the loss of its water of crystallization. Its solution is strongly 
alkaline. A third tribasic phosphate, often called superphosphate or biphos- 
phate, NaO,2HO,P0 5 -|-2HO, may be obtained by adding phosphoric acid to 
the ordinary phosphate, until it ceases to precipitate chloride of barium, and 
exposing the concentrated solution to cold. The crystals are prismatic, very 
soluble, and have an acid reaction. When strongly heated, the salt becomes 
changed into monobasic phosphate of soda. 

Tribasic phosphate of soda, ammonia, and water ; microcosmic salt, NaO, 
NH 4 0,HO,P0 5 -4-8HO. — Six parts of common phosphate of soda are heated 
with 2 of water until the whole is liquefied, when 1 part of powdered sal- 
ammoniac is added ; common salt separates, and may be removed by a filter, 
and from the solution, duly concentrated, the new salt is deposited in pris- 
matic crystals, which may be purified by one or two re-crystallizations. 
Microcosmic salt is very soluble. When gently heated, it parts with the 8 
eq. of water crystallization, and, at a higher temperature, the water acting 
as base is expelled, together with the ammonia, and a very fusible compound, 
metaphosphate of soda, remains, which is valuable as a flux in blowpipe ex- 
periments. This salt is said to occur in the urine. 

Bibasic phosphate of soda; pyrophosphate of soda, 2 NaO,PO 5 -4-10HO. 
— Prepared by strongly heating common phosphate of soda, dissolving the 
residue in water, and re-crystallizing. The crystals are very brilliant, per- 
manent in the air, and less soluble than the original phosphate ; their solution, 
is alkaline. A bibasic phosphate, containing an equivalent of basic water, 
has been obtained ; it does not, however, crystallize. 

Monobasic phosphate of soda; metaphosphate of soda, NaO,P0 5 . — 
Obtained by heating either the acid tribasic phosphate, or microcosmic salt. 
It is a transparent glassy substance, fusible at a dull red-heat, deliquescent, 
and very soluble in water. It refuses to crystallize, but dries up into a 
gum-like mass. 

If this glassy phosphate be cooled very slowly a beautifully crystalline 
mass is obtained. It may be separated by means of boiling water from the 
vitreous metaphosphate which will not crystallize. Another metaphosphate 
has been obtained by adding sulphate of soda to an excess of phosphoric acid, 
evaporating and heating to upwards of C00° (315°-5C). Possibly these 



SODIUM. 231 

several metamosphates may be represented by the formulce NaO,P0 5 ; 
2NaO,2P0 5 ; 3NaO,3P0 5 . 

The tribasic phosphates give a bright yellow precipitate -with solution of 
nitrate of silver ; the bibasic and monobasic phosphates afford white precipi- 
tates with the same substance. The salts of the two latter classes, fused 
with excess of carbonate of soda, yield the tribasic modification of the acid. 

Phosphates intermediate between the monobasic and bibasic phosphates of soda, 
8XaO,2P0 5 , and 6NaO,5P0 5 . — The first is produced by fusing 100 parts of 
anhydrous pyrophosphate of soda, and 76-87 parts of metaphosphate of soda. 
The white crystalline mass is reduced to powder, and quickly exhausted with 
water. The solution, on exposure to the atmosphere, yields small plates which 
are very soluble in water. 

The second is produced by fusing 100 parts of pyrophosphate of soda, and 
307-5 of metaphosphate; it crystallizes with more difficulty than the prece- 
ding compound. 

MM. Fleitmann and Henneberg, the discoverers of these new phosphates, 
represent the different phosphates thus : — 



Common phosphate 6NaO,2P0 5 

Pyrophosphate 6NaO,3P0 5 

New phosphates {txloMZl 

Metaphosphate 6NaO,6P0 6 



In each of which six equivalents of the base are combined with a different 
polymeric acid. 

Biborate of soda; borax, NaO,2B0 3 -f- 10HO. — This compound occurs 
in the waters of certain lakes in Thibet and Persia ; it is imported in a crude 
state from the East Indies under the name of tincal. "When purified, it con- 
stitutes the borax of commerce. Much borax is now, however, manufactured 
from the native boracic acid of Tuscany. Borax crystallizes in six-sided 
prisms, which effloresce in dry air, and require 20 parts of cold, and 6 of 
boiling water for solution. Exposed to heat, the 10 eq. of water of crystal- 
lization are expelled, and at a higher temperature the salt fuses, and assumes 
a glassy appearance on cooling ; in this state it is much used for blowpipe 
experiments, the metallic oxides dissolving in it to transparent beads, many 
of which are distinguished by characteristic colours. By particular manage- 
ment, crystals of borax can be obtained with 5 eq. of water ; they are very 
hard, and permanent in the air. Although by constitution an acid salt, 
borax has an alkaline reaction to test-paper. It is used in the arts for sol- 
dering metals, its action consisting in rendering the surfaces to be joined 
metallic, by dissolving the oxides, and sometimes enters into the composition 
of the glaze with which stoneware is covered. 

Neutral borate of soda may be formed by fusing together borax and car- 
bonate of soda in equivalent proportions, and then dissolving the mass in 
water. The crystals are large, and contain NaO,B0 3 -J-8HO. 

Sulphide of sodium, NaS. — Prepared in the same manner as the proto- 
stilphide of potassium ; it separates from a concentrated solution in octahe- 
dral crystals, which are rapidly decomposed by contact of air into a mixture 
of hydrate and hyposulphite of soda, It forms double sulphur-salts with 
sulphuretted hydrogen, bisulphide of carbon, and other sulphur-acids. 

Sulphide of sodium is supposed to enter into the composition of the beau- 
tiful pigment ultramarine, prepared from the lapis lazuli, and which is now 
)raitated by artificial means. 1 

Chloride of sodium ; common salt, NaCl. — This very important sub- 

1 See Pharmaceutical Journal, ii. 53. 



232 AMMONIUM. 

stance is found in many parts of the world in solid beds or irregular strata 
of immense thickness, as in Cheshire, for example, in Spain, Galicia, and 
many other localities. An inexhaustible supply exists also in the waters of 
the ocean, and large quantities are annually obtained from saline springs. 

The rock-salt is almost always too impure for use ; if no natural brine- 
spring exist, an artificial one is formed by sinking a shaft into the rock-salt, 
and, if necessary, introducing water. This, when saturated, is pumped up, 
and evaporated more or less rapidly in large iron pans. As the salt sepa- 
rates, it is removed from the bottom of the vessels by means of a scoop, 
pressed while still moist into moulds, and then transferred to the drying- 
stove. When large crystals are required, as for the coarse-grained bay-salt 
used in curing provisions, the evaporation is slowly conducted. Common 
salt is apt to be contaminated with chloride of magnesium. 

When pure, this substance is not deliquescent in moderately dry air. It 
crystallizes in anhydrous cubes, which are often grouped together into pyra- 
mids, or steps. It requires about 1\ parts of water at 60° (15°-5C) for solu- 
tion, and its solubility is not sensibly increased by heat; it dissolves to some 
extent in spirits, but is nearly insoluble in absolute alcohol. Chloride of 
sodium fuses at a red-heat, and is volatile at a still higher temperature. The 
economical uses of common salt are well known. 

The iodide and bromide of sodium much resemble the corresponding potas- 
sium-compounds : they crystallize in cubes which are anhydrous, and are 
very soluble in water. 



There is no good precipitant for soda, all the salts being very soluble with 
the exception of antimonate of soda, the use of which is attended with diffi- 
culties ; its preseilce is often determined by purely negative evidence. The 
yellow colour imparted by soda-salt to the outer flame of the blowpipe, and 
to combustible matter, is a character of some importance. 

AMMONIUM. 

In connection with the compounds of potassium and sodium, those formed 
by ammonia are most conveniently studied. Ammoniacal salts correspond 
in every respect in constitution with those of potassa and soda ; in all cases 
the substance which replaces those alkalis is hydrate of ammonia, or, as it 
is now almost generally considered, the oxide of a hypothetical substance 
called ammonium, capable of playing the part of a metal, and ismorphous 
with potassium and sodium. All attempts to isolate this substance have 
failed, apparently from its tendency to separate into ammonia and hydrogen 
gas. 

When a globule of mercury is placed on a piece of moistened caustic po- 
tassa, and connected with the negative side of a voltaic battery of very 
moderate power, while the circuit is completed through the platinum plate 
upon which rests the alkali, decomposition of the latter takes place, and an 
amalgam of potassium is rapidly formed. 

If this experiment be now repeated with a piece of sal-ammoniac instead 
of hydrate of potassa, a soft solid, metalline mass is also produced, which 
has been called the ammoniacal amalgam, and considered to contain ammo- 
nium in combination with mercury. A still simpler method of preparing 
this extraordinary compound is the following: — A little mercury is put into 
a test-tube with a grain or two of potnssium or sodium, and gentle heat ap- 
plied ; combination ensues, attended by heat and light. When cold, the 
fluid amalgam is put into a capsule, and covered with a strong solution of 
*al-:unmoniac. The production of ammoniacal amalgam instantly com- 
mences, the mercury increases prodigiously in vilume, and becomes quite 



AMMONIUM. 233 

pasty. The increase of weight is, however, quite trifling ; it varies from 

nnro th to T2flTro th P art - 

Left to itself, the amalgam quickly decomposes into fluid mercury, ammo- 
nia, and hydrogen. 

It is difficult to offer any opinion concerning the real nature of this com- 
pound: something analogous occurs when pure silver is exposed to a very 
high temperature, much above its melting-point, in contact with air or oxv- 
gen gas ; the latter is absoi'bed in very large quantity, amounting, accord • 
ing to the observation of Gay-Lussac, to 20 times the volume of the silver, 
and is again disengaged on lessening the heat. The metal loses none of its 
lustre, and is not sensibly altered in other respects. 

The great argument in favour of the existence of ammonium is founded 
on the perfect comparison which the ammoniacal salts bear with those of 
the alkaline metals. 

The equivalent of ammonium is 18; its symbol is NH 4 . 

Chloride of ammonium; (Mubiate of Ammonia;) sal-ammoniac, NH 4 C1. 
— Sal-ammoniac was formerly obtained from Egypt, being extracted by sub- 
limation from the soot of camels' dung; it is now largely manufactured from 
the ammoniacal liquid of the gas-works, and from the condensed products 
of the distillation of bones, and other animal refuse, in the preparation of 
animal charcoal. 

These impure and highly offensive solutions are treated with slight excess 
of hydrochloric acid, by which the alkali is neutralized, and the carbonate 
and sulphide decomposed with evolution of carbonic acid and sulphuretted 
l^di'ogen gases. The liquid is evaporated to dryness, and the salt carefully 
heated, to expel or decompose the tarry matter ; it is then purified by sub- 
limation in lai'ge iron vessels lined with clay, surmounted with domes of lead. 

Sublimed sal-ammoniac has a fibrous texture, it is tough, and difficult to 
powder. 

When crystallized from water it separates under favourable circumstances, 
in distinct cubes or octahedrons ; but the crystals are usually small, and ag- 
gregated together in rays. It has a sharp saline taste, and is soluble in 2f 
parts of cold, in a much smaller quantity of hot water. By heat, it is sub- 
limed without decomposition. The crystals are anhydrous. Chloride of 
ammonium forms double salts with chloride of magnesium, nickel, cobalt, 
manganese, zinc, and copper. 

Sulphate op oxide op ammonium ; sulphate of ammonia, NH 4 0, 
S0 3 -j-HO. — Prepared by neutralizing carbonate of ammonia by sulphuric 
acid, or on a large scale, by adding sulphuric acid in excess to the coal-gas 
liquor just mentioned, and purifying the product by suitable means. It is 
soluble in 2 parts of cold water, and crystallizes in long, flattened, six-sided 
prisms, which lose an equivalent of water when heated. It is entirely de- 
composed, and driven off by ignition, and, even to a certain extent, by long 
boiling with water, ammonia being expelled and the liquid rendered acid. 

Carbonates op ammonia. — These compounds have been carefully exam- 
ined by Professor Rose, of Berlin, 1 and appear very numerous. The neutral, 
anhydrous carbonate, NH 3 ,C0 2 , is prepared by the direct union of carbonic 
acid with ammoniacal gas, both being carefully cooled. The gases combine 
in the proportions of one measure of the first to two of the second, and give 
rise to a pungent, and very volatile compound, which condenses in white 
flocks. It is very soluble in water. The pungent, transparent, carbonate 
of ammonia of pharmacy, which is prepared by subliming a mixture of sal- 
ammoniac and chalk, always contains less base than that required to form 
a neutral carbonate. Its composition varies a good deal, but in freshly pre- 

1 Annalen der Pharmacie, xxx. 45 

20* 



234 AMMONIUM. 

pared specimens approaches that of a sesquicarbonate of oxide of ammonium, 
2 NH 4 0,3C0 2 . — When heated in a retort, the neck of which dips into mer- 
cury, it is decomposed, with disengagement of pure carbonic acid, into 
neutral hydrated carbonate of ammonia, and several other compounds. Ex- 
posed to the air at common temperatures, it disengages neutral carbonate 
of ammonia, loses its pungency, and crumbles down to a soft, white powder, 
which is a bicarbonate, containing NH 4 0,C0 2 -}-HO,C0 2 . This is a permanent 
combination, although still volatile. When a strong solution of the commer- 
cial sesquicarbonate is made with tepid water, and filtered, warm, into a 
close vessel, large and regular crystals of bicarbonate, having the above com- 
position, are sometimes deposited after a few days. These are inodorous, 
quite permanent in the air, and resemble, in the closest manner, crystals of 
bicarbonate of potassa. 

Nitrate of oxide of Ammonium; nitrate of ammonia, NIT 4 0,N0 5 . — 
Easily prepared by adding carbonate of ammonia to slightly diluted nitric 
acid until neutralization has been reached. Ey slow evaporation at a mode- 
rate temperature it crystallizes in six-sided prisms, like those of nitrate of 
potassa ; but, as usually prepared for making nitrous oxide, by quick boiling, 
until a portion solidifies completely on cooling, it forms a fibrous and indis- 
tinct crystalline mass. 

Nitrate of ammonia dissolves in 2 parts of cold water, is but feebly deli- 
quescent, and deflagrates like nitre on contact with heated combustible 
matter. Its decomposition by heat has been already explained. 1 

Sulphides of Ammonium. — Several of these compounds exist, and may 
be formed by distilling with sal-ammoniac the corresponding sulphides of 
potassium or sodium. 

The double sulphide of ammonium and hydrogen, NH 4 S-j-HS, commonly 
called hydrosulphate of ammonia, or, more correctly, hydrosulphate of sul- 
phide of ammonium, is a compound of great practical utility ; it is obtained 
by saturating a solution of ammonia with well- washed sulphuretted hydrogen 
gas, until no more of the latter is absorbed. The solution is nearly colourless 
at first, but becomes yellow after a time, without, however, suffering material 
injury, unless it has been exposed to the air. It gives precipitates with most 
metallic solutions, which are very often characteristic, and is of great service 
in analytical chemistry. 2 



When dry ammoniacal gas is brought in contact with anhydrous sulphuric 
acid, a white crystalline compound is produced, which is soluble in water. 
In a freshly prepared cold solution of this substance neither sulphuric acid 
nor ammonia can be fouud ; but after standing some time, and especially if 
heat be applied, it passes into ordinary sulphate of ammonia. 

A compound of dry ammoniacal gas and sulphurous acid also exists ; it is 
a yellow soluble substance, altogether distinct from sulphite of ammonia. 

4 Page 125. 

a PHOSPHATES OP OXIDE OF AMMONIUM; COMMON TEIBASIC PHOSPHATE, 2 NITiOJIO.POs-f HO. — 

This salt is formed by precipitating the acid phosphate of lime with an excess of carbonate 
of ammonia. The solution is allowed to evaporate spontaneously or by a gentle heat. In 
the hitter case ammonia is lost and it becomes necessary to saturate the acid set free, previous 
to crystallization. It crystallizes in six-sided tables derived from oblique quadrangular 
prisms. Its crystals are efflorescent, soluble in alcohol, and soluble in four times its weight 
of cold water. Its solution has an alkaline, slightly saline taste and alkaline reaction. Ey 
heat ammonia is disengaged. 

The acid tribasic phosphate, NII4O.21IO.PO5+4IIO. is formed when a solution of the common 
phosphate is boiled as long as ammonia is given off. It crystallizes in four-sided prisms. Its 
crystals are permanent, soluble in 5 parts of cold water, acid in taste and reaction. 

Another trihasio phosphate, 3NH40,P06 subphospbate is formed by adding ammonia lo 
either ot'ine above it falls as a slightly soluble granular precipitate— R. li. 



LITHIUM. 235 

Dry carbonic acid and ammonia also unite to form a volatile white powder, 
as already mentioned. 

When certain salts, especially chlorides in an anhydrous state, are exposed 
to ammoniacal gas, the latter is absorbed with great energy, and the combi- 
nations formed are not alwaj-s easily decomposed by heat. The chlorides of 
copper and silver absorb, in this manner, large quantities of the gas. All 
these compounds must be carefully distinguished from the true ammoniacal 
salts containing ammonium or its oxide. 



There is supposed to be yet another compound of hydrogen and nitrogen 
to which the term amidogen has been given. When potassium is heated in 
the vapour of water, this substance is decomposed, hydrogen is evolved, and 
the metal converted into oxide. When the same experiment is made with 
dry ammoniacal gas, hydrogen is also set free, and an olive-green crystalline 
compound produced, supposed to contain potassium in union with a new body, 
NH 2 , having an equivalent of hydrogen less than ammonia. 

When ammonia is added to a solution of corrosive sublimate, a white pre- 
cipitate is obtained, which has been long known in pharmacy. Sir R. Kane 
infers, from his experiments, that this substance should be looked upon as a 
compound of chloride of mercury with amide of mercury. The latter salt 
has not been obtained separately ; still less has amidogen itself been isolated. 

It has been thought that ammonia may be considered an amide of hydrogen, 
analogous to water or oxide of hydrogen, capable of entering into combina- 
tion with salts, and other substances, in a similar manner, yielding unstable 
and easily decomposed compounds, which offer a great contrast to those of 
the energetic quasi-metal ammonium ; the views of chemists upon this sub- 
ject are, however, still divided. 



The ammoniacal salts are easily recognised ; they are all decomposed or 
volatilized by a high temperature ; and when heated with hydrate of lime, 
or solution of alkaline carbonate, evolve ammonia, which may be known by 
its odour and alkaline reaction. The salts are all more or less soluble, the 
acid tartrate of ammonia and the double chloinde of ammonium and platinum 
being among the least so ; hence the salts of ammonia cannot be distinguished 
from those of potassa by the tests of tartaric acid and platinum-solution. 

LITHIUM. 

A connecting link between this class of metals and the next succeeding. 
Lithium is obtained by electrolyzing, in contact with mercury, the hydrate 
of lithia, and then decomposing the amalgam by distillation. It is a white 
metal like sodium, and very oxidable. The equivalent of lithium is 6-5, and 
its symbol L. 

The oxide, lithia, LO, is found in petalite, spodumene, lepidolite, and a 
few other minei^als, and sometimes occurs in minute quantities in mineral 
springs. From petalite it may be obtained, on the small scale, by the fol- 
lowing process : — The mineral is reduced to an exceedingly fine powder, 
mixed with five or six times its weight of pure carbonate of lime, and the 
mixture heated to whiteness, in a platinum crucible, placed within a well- 
covered earthen one, for twenty minutes or half an hour. The shrunken 
coherent mass is digested in dilute hydrochloric acid, the whole evaporated 
to dryness, acidulated water added, and the silica separated by a filter. Tf e 
solution is then mixed with carbonate of ammonia in excess, boiled and 
filtered ; the clear liquid is evaporated to dryness, and gently heated in a 



236 l i t n i u m . 

platinum crucible, to expel the sal-ammoniac. The residue is then wetted 
■with oil of vitriol, gently evaporated once more to dryness, and ignited ; 
pure fused sulphate of lithia remains. 

This process will serve to give a good idea of the general nature of the 
operation by which alkalis are extracted in mineral analysis, and then 
quantities determined. 

The hydrate of lithia is much less soluble in water than those of potassa 
and soda; the carbonate and phosphate are also spai-ingly soluble salts. 
The chloride crystallizes in anhydrous cubes which are deliquescent. Sul- 
phate of lithia is a very beautiful salt ; it crystallizes in lengthened prisms 
containing one equivalent of water. It gives no double salt with sulphate 
of alumina. 

The salts of lithia colour the outer flame of the blowpipe carmine-red. 



BARIUM. 237 



SECTION II. 
METALS OF THE ALKALINE EARTHS. 



Barium was obtained by Sir H. Davy by means similar to those mentioned 
in the case of lithium ; it is procured more advantageously, by strongly heat- 
ing baryta in an iron tube, through which the vapour of potassium is con- 
veyed. The reduced barium is extracted by quicksilver, and the amalgam 
distilled in a small green glass retort. 

Barium is a white metal, having the colour and lustre of silver ; it is mal- 
leable, melts below a red heat, decomposes water, and gradually oxidizes in 
the air. 

The equivalent of this metal has been fixed at 68-5 ; its symbol is Ba. 

Protoxide of barium; baryta, BaO. — Baryta, 1 or barytes, occurs in 
nature in considerable abundance as carbonate and sulphate, forming the 
veinstone in many lead-mines ; from both these sources it may be extracted 
with facility. The best method of preparing pure baryta is to decompose 
the crystallized nitrate by heat in a capacious crucible of porcelain until red 
vapours are no longer disengaged ; the nitric acid is resolved into nitrous 
acid and oxygen, and the baryta remains behind in the form of a greyish 
spongy mass, fusible at a high degree of heat. When moistened with water, 
it combines to a hydrate with great elevation of temperature. 

The hydrate is a white, soft powder, having a great attraction for carbonic 
acid, and soluble in 20 parts of cold and 2 of boiling water ; a hot saturated 
solution deposits crystals on cooling, which contain BaO, HO-f-9HO. Solu- 
tion of hydrate of baryta is a valuable re-agent ; it is highly alkaline to 
test-paper, and instantly rendered turbid by the smallest trace of. carbonic 
acid. 

Binoxide of barium, Ba0 2 . — This may be formed, as already mentioned, 
by exposing baryta, heated to full redness in a porcelain tube, to a current 
of pure oxygen gas. The binoxide is grey, and forms a white hydrate with 
water, which is not decomposed by that liquid in the cold, but dissolves in 
small quantity. The binoxide may also be made by heating pure baryta to 
redness in a platinum crucible, and then gradually adding an equal weight 
of chlorate of potassa ; binoxide of barium and chloride of potassium are 
produced. The latter may be extracted by cold water, and the binoxide 
left in the state of hydrate. It is interesting chiefly in its relation to bin- 
oxide of hydrogen. When dissolved in dilute acid, it is decomposed by 
bichromate of potassa, oxide of silver, chloride of silver, sulphate and car 
bonate of silver. 

Chloride of barium, BaCl-j-2HO. — This valuable salt is prepared by 
dissolving the native carbonate in hydrochloric acid, filtering the solution, 

1 From @apvs, heavy, in allusion to the great specific gravity of the native carbonate and 
6ulphate. 



238 BARIUM. 

and evaporating until a skin begins to form at the surface ; the solution on 
cooling deposits crystals. When native carbonate cannot be procured, the 
native sulphate may be employed in the following manner: — The sulphate is 
reduced to fine powder, and intimately mixed with one-third of its weight 
of powdered coal ; the mixture is pressed into an earthen crucible to which 
a cover is fitted, and exposed for an hour or more to a high red-heat, by 
which the sulphate is converted into sulphide at the expense of the com- 
bustible matter of the coal. The black mass obtained is powdered and boiled 
in water, by which the sulphide is dissolved ; the solution is filtered hot, and 
mixed with a slight excess of hydrochloric acid ; chloride of barium and sul- 
phuretted hydrogen are produced ; the latter escaping with effervescence. 
Lastly, the solution is filtered to separate any little insoluble matter, and eva- 
porated to the crystallizing point. 

The crystals of chloride of barium are flat, four-sided tables, colourless 
and transparent. They contain 2 equivalents of water, easily driven off by 
heat; 100 parts of water dissolve 43-5 parts at 60° (15°-5C), and 78 parts 
at 223° (106° -5C), which is the boiling-point of the saturated solution. 

Nitrate of baryta, BaO, N0 5 . — The nitrate is prepared by methods 
exactly similar to the above, nitric acid being substituted for the hydro- 
chloric. It crystallizes in transparent colourless octahedrons, which are 
anhydrous. They require for solution 8 parts of cold, and 3 parts of boil- 
ing water. This salt is much less soluble in dilute nitric acid than in pure 
water ; errors sometimes arise from such a precipitate of crystalline nitrate 
of baryta being mistaken for sulphate. It disappears on heating, or by large 
affusion of water. 

Sulphate of baryta; heavy-spar; BaO,S0 3 . — Found native, often beau- 
tifully crystallized. This compound is always produced when sulphuric acid 
or a soluble sulphate is mixed with a solution of a barytic salt. It is not 
sensibly soluble in water or in any dilute acid, even nitric ; hot oil of vitriol 
dissolves a little, but the greater part separates again on cooling. Sulphate 
of baryta is used as a pigment, but often for the purpose of adulterating 
white-lead ; the native salt is ground to fine powder and washed Avith dilute 
sulphuric acid, by which its colour is improved, and a little oxide of iron 
probably dissolved out. The specific gravity of the natural sulphate is as 
high as 4-4 to 4-8. 

Sulphide of barium, BaS. — The protosulphide of barium is obtained in 
the manner already described; the higher sulphides may be formed by boil- 
ing this compound with sulphur. Protosulphide of barium crystallizes in 
thin and' nearly colourless plates from a hot solution, which contain water, 
and are not very soluble ; they are rapidly altered by the air. A strong 
solution of sulphide may be employed in the preparation of hydrate of baryta, 
by boiling it with small successive portions of black oxide of copper, until a 
drop of the liquid ceases to precipitate a salt of the lead black; the liquid 
being filtered, yields, on cooling, crystals of hydrate. In this reaction, besides 
hydrate of baryta, hyposulphite of that base, and sulphide of copper are 
produced ; the latter is insoluble, and is removed by the filter, while most 
of the hyposulphite remains in the mother-liquor. 

Carbonate of baryta, BaO, C0 2 . — The natural carbonate is called ivitke- 
rite; the artificial is formed by precipitating the chloride or nitrate with an 
alkaline carbonate, or carbonate of ammonia. It is a heavy, white powder, 
Very sparingly soluble in water, and chiefly useful in the preparation of the 
rarer baryta-salts. 



Solutions of hydrate and nitrate of baryta and of the chloride of barium 
are constantly kept in the laboratory as chemical tests, the first being em- 



STRONTIUM. 239 

ployed to effect the separation of carbonic acid from certain gaseous mix- 
tures, and the two latter to precipitate sulphuric acid from solution. 

The soluble salts of baryta are poisonous, -which is not the case with 
those of the base next to be described. 

STRONTIUM. 

The metal strontium may be obtained from its oxide by means similar to 
those described in the case of barium ; it is a white metal, heavy, oxidizable 
n the air, and capable of decomposing water at common temperatures. 

The equivalent of strontium is 43-8, and its symbol is Sr. 

Protoxide of strontium ; strontia ; SrO. — This compound is best pre- 
pared by decomposing the nitrate by the aid of heat; it resembles in almost 
every particular the earth baryta, forming, like that substance, a white hy- 
drate, soluble in water. A hot saturated solution deposits crystals on cool- 
ing, which contain 10 equivalents of water. The hydrate has a great at- 
traction for carbonic acid. 

Binoxide of strontium, Sr0 2 . — The binoxide is prepared in the same 
manner as binoxide of barium ; it may be substituted for the latter in mak- 
ing binoxide of hydrogen. 

The native carbonate and sulphate of strontia, met with in lead-mines and 
other localities, serve for the preparation of the various salts by means ex- 
actly similar to those already described in the case of baryta ; they have a 
very feeble degree of solubility in water. 

Chloride of strontium, SrCl. — The chloride crystallizes in colourless 
needles or prisms, which are slightly deliquescent, and soluble in 2 parts of 
cold and still less of boiling water ; they are also soluble in alcohol, and the 
solution, when kindled, burns with a crimson flame. The crystals contain 6 
equivalents of water, which they lose by heat ; at a higher temperature the 
chloride fuses. 

Nitrate of strontia, SrO,N0 5 . — This salt crystallizes in anhydrous oc- 
tahedrons, which require for solution 5 parts of cold, and about half their 
weight of boiling water. It is principally of value to the pyrotechnist, who 
employs it in the composition of the well-known "red-fire." l 



This is a silver-white and extremely oxidable metal, obtained with great 
difficulty by means analogous to those by which barium and strontium are 
procured. 

The equivalent of calcium is 20 ; its symbol is Ca. 

Protoxide of calcium ; lime ; CaO. — This extremely important com- 
pound may be obtained in a state of considerable purity by heating to full 
redness, for some time, fragments of the black bituminous marble of Derby, 
shire or Kilkenny. If required absolutely pure, it must be made by ignit- 
ing to whiteness, in a platinum crucible, an artificial carbonate of lime, pro- 
cured by precipitating the nitrate by carbonate of ammonia. Lime in an 
impure state is prepared for building and agricultural purposes by calcining 



Red-Fire : — Grns. 

Dry nitrate of strontia 800 

Sulphur 225 

Chlorate of potassa 200 

Lampblack 50 



Green-Fire : — Grna . 

Dry nitrate of baryta 4oc 

Sulphur 150 

Chlorate of potassa 100 

Lampblack 25 



The strontia or baryta-salt, the sulphur, and the lampblack, must be finely powdered and 
intimately mixed, after which the chlorate of potassa should be added in rather coarse pow- 
der, and mixed without much rubbing with the other ingredients. The red-fire composition 
has teen known to ignite spontaneously. 



240 CALCIUM. 

in a kiln of suitable construction, the ordinary limestones which abound in 
many districts ; a red-heat, continued for some hours, is sufficient to disen- 
gage the whole of the carbonic acid. In the best contrived lime-kilns the 
process is carried on continuously, broken limestone and fuel being con- 
stantly thrown in at the top, and the burned lime raked out at intervals from 
beneath. Sometimes, when the limestones contain silica, and the heat has 
been very high, the lime refuses to slake, and is said to be over-burned ; in 
this case a portion of silicate has been formed. 

Pure lime is white, and often of considerable hardness ; it is quite infusi- 
ble, and phosphoresces, or emits a pale light at a high temperature. When 
moistened with water, it slakes with great violence, evolving heat, and 
crumbling to a soft, white, bulky powder, which is a hydrate containing a 
single equivalent of water ; the latter can be again expelled by a red-heat. 
This hydrate is soluble in water, but far less so than either the hydrate of 
baryta or of strontia, and what is very remarkable, the colder the water, the 
larger the quantity of the compound which is taken up. A pint of water at 
60° (15° -5C) dissolves about 11 grains, while at 212° (100°C) only 7 grains 
are retained in solution. The hydrate has been obtained in thin delicate 
crystals by slow evaporation under the air-pump. Lime-water is always 
prepared for chemical and pharmaceutical purposes by agitating cold water 
with excess of hydrate of lime in a closely-stopped vessel, and then, after 
subsidence, pouring off the clear liquid, and adding a fresh quantity of 
water, for another occasion ; — there is not the least occasion for filtering the 
solution. Lime-water has a strong alkaline reaction, a nauseous taste, and 
when exposed to the air becomes almost instantly covered with a pellicle of 
carbonate, by absorption of carbonic acid from the atmosphere. It is used, 
like baryta-water, as a test for that substance, and also in medicine. Lime- 
water prepared from some varieties of limestone may contain potassa. 

The hardening of mortars and cements is in a great measure due to the 
gradual absorption of carbonic acid ; but even after a very great length of 
time, this conversion into carbonate is not complete. Mortar is known, 
under favourable circumstances, to acquire extreme hardness with age. 
Lime-cements which resist the action of water, contain the oxides of iron, 
silica, and alumina ; they require to be carefully prepared, and the stone not 
over-heated. When ground to powder and mixed with water, solidification 
speedily ensues, from causes not yet thoroughly understood, and the cement, 
once in this condition, is unaffected by wet. Parker's or Roman cement is 
made in this manner from the nodular masses of calcareo-argillaceous iron- 
stone found in the London clay. Lime is of great importance in agriculture ; 
it is found more or less in every fertile soil, and is often very advantageously 
added by the cultivator. The decajr of vegetable fibre in the soil is promoted, 
and other important objects, as the destruction of certain hurtful compounds 
of iron in marsh and peat-land, is often attained. The addition of lime pro- 
bably serves likewise to liberate potassa from the insoluble silicate of that 
base contained in the soil. 

Binoxide of Calcium, Ca0 2 . — This is stated to resemble binoxide of 
barium, and to be obtainable by a similar process. 

Chloride of calcium, CaCl. — Usually prepared by dissolving marble in 
hydrochloric acid ; also a by-product in several chemical manufactures. The 
salt separates from a strong solution in colourless, prismatic, and exceed- 
ingly deliquescent crystals, which contain 6 equivalents of water. By heat 
this water is expelled, and by a temperature of strong ignition the salt is 
fused. The crystals reduced to powder are employed in the production of 
artificial cold by being mixed with snow or powdered ice ; and the chloride, 
strongly dried or in a fused condition, is of great practical use in desiccating 
gases, for which purpose the latter are slowly transmitted through tubes 



CALCIUM. 211 

filled with fragments of the salt. Chloride of calcium is also freely soluble 
in alcohol, which, when anhydrous, forms with it a definite crystallizable 
compound. 

Sulphide of calcium. — The simple sulphide is obtained by reducing 
sulphate of lime at a high temperature by charcqal or hydrogen ; it is nearly 
colourless, and but little soluble in water. — By boiling together hydrate of 
lime, water, and flowers of sulphur, a red solution is obtained, which on 
cooling deposits crystals of bisulphide, which contain water. When the 
sulphur is in excess, and the boiling long continued, a pentasulphide is 
generated ; hyposulphurous acid is, as usual, formed in these reactions. 

Phosphide op calcium. — When the vapour of phosphorus is passed over 
fragments of lime heated to redness in a poi-celain tube, a chocolate-brown 
compound, the so-called phosphide of lime, is produced. This substance is 
probably a mechanical mixture of phosphide of calcium, and phosphate of 
lime. It yields spontaneously inflammable phosphoretted hydrogen when 
put into water. 1 

Sulphate of lime ; gypsum ; selenite ; CaO, S0 3 . — Native sulphate of 
lime in a crystalline condition, containing 2 equivalents of water, is found in 
considerable abundance in some localities ; it is often associated with rock- 
salt. When regularly crystallized, it is termed selenite. Anhydrous sulphate 
of lime is also occasionally met with. The salt is formed by precipitation 
when a moderately concentrated solution of chloride of calcium is mixed 
with sulphuric acid. Sulphate of lime is soluble in about 500 parts of cold 
water, and its solubility is a little increased by heat. It is more soluble in 
water containing chloride of ammonium or nitrate of potassa. The solution 
is precipitated by alcohol. Gypsum, or native hydrated sulphate, is largely 
employed for the purpose of making casts of statues and medals, and also 
for moulds in the porcelain and earthenware manufactures, and for other 
applications. It is exposed to heat in an oven where the temperature does 
not exceed 260° (126°-6C), by which the water of crystallization is expelled, 
and afterwards reduced to fine powder. When mixed with water, it solidifies 
after a short time from the re-formation of the same hydrate ; but this effect 
does not happen if the gypsum has been over-heated. It is often called 
plaster of Paris. Artificial coloured marbles, or scagliola, are frequently 
prepared by inserting pieces of natural stone in a soft stucco containing this 
substance, and polishing the surface when the cement has become hard. 
Sulphate of lime is one of the most common impurities of spring water. 

The peculiar property water acquires by the presence in it of lime, is 
termed hardness. It manifests itself by the effect such waters have upon 
the palate, and particularly by its peculiar behaviour with soap. Hard 
waters yield a lather with soap only after the whole of the lime-salts have 
been thrown down from the water in the form of an insoluble lime-soap. 
Upon this principle, Prof. Clark's soap-test for the hardness of waters is 
based. 2 The hardness produced by sulphate of lime is colled permanent hard- 
ness, since it cannot be remedied. 

Carbonate of lime ; chalk ; limestone ; marble ; CaO, C0 2 . — Carbo- 
nate of lime, often more or less contaminated by protoxide of iron, clay, and 
organic matter, forms rocky beds, of immense extent and thickness, in 
almost every part of the world. These present the greatest diversities of 
texture and appearance, arising, in a great measure, from changes to which 

1 According to M. Paul Thenard, the phosphide of calcium existing in this mixture, has 
the compositions PCas. Bv coming in contact with water, it yields liquid phosphoretted 
hydrogen, PCa 2 + 2IIO = 2CaO + PH 2 — (Page 166). 

The greater portion of the liquid phosphide is immediately decomposed into solid and 
gaseous phosphoretted hydrogen. — 5PH2 = 3PH3 + P 2 H. 

a Journal of the Pharmaceutical Society, vol. vi. p. 526. 



242 CALCIUM. 

they have been subjected since their deposition. The most ancient and 
highly crystalline limestones are destitute of visible organic remains, while 
those of more recent origin are often entirely made up of the shelly exuvis 
of once living beings. Sometimes these latter are of such a nature as to 
show that the animals inhabited fresh water ; marine species and corals are, 
however, most abundant. Cavities in limestone and other rocks are very 
often lined with magnificent crystals of carbonate of lime or calcareous spar, 
which have evidently been slowly deposited from a watery solution. Carbo- 
nate of lime is always precipitated when an alkaline carbonate is mixed with 
a solution of that base. 

Although this substance is not sensibly soluble in pure water, is is freely 
taken up when carbonic acid happens at the same time to be present. If a 
little lime-water be poured into a vessel of that gas, the turbidity first pro- 
duced disappears on agitation, and a transparent solution of carbonate of 
lime in excess of carbonic acid is obtained. This solution is decomposeo 
completely by boiling, the carbonic acid being expelled, and the carbonate 
precipitated. Since all natural waters contain dissolved carbonic acid, it if 
to be expected that lime in this condition should be of very common occur- 
rence ; and such is really found to be the fact ; river, and more especiallj 
spring water, almost invariably containing carbonate of lime thus dissolved 
In limestone districts, this is often the case to a great extent. The hardnesi 
of water, which is owing to the presence of carbonate of lime, is called tem- 
porary, since it is diminished to a very considerable extent by boiling, and 
may be nearly removed by mixing the hard water with lime-water, when both 
the dissolved carbonate and the dissolved lime, which becomes thus carbo- 
nated, are precipitated. Upon this principle, Prof. Clark's process of soft- 
ening water is based. This process is of considerable importance, since a 
supply of hard water to towns is in many respects a source of great inconve- 
nience. As has been already mentioned, the use of such water, for the pur- 
poses of washing, is attended with a great loss of soap. Boilers in which 
such water is heated, speedily become lined with a thick stony incrustation. 1 
The beautiful stalactitic incrustations of lime-stone caverns, and the deposits 
of calc-sinter or travertin upon various objects, and upon the ground in many 
places, are thus explained by the solubility of carbonate of lime in water 
containing carbonic acid. 

Crystallized carbonate of lime exhibits the curious property of dimorphism ; 
calcareous spar and arragonite, although possessing the same chemical com- 
position, both containing single equivalents of lime and carbonic acid, and 
nothing besides, have different crystalline forms, different densities, and dif- 
ferent optical properties. 

The former occurs very abundantly in crystals derived from an obtuse 
rhomboid, whose angles measure 105° 5' and 74° 55 7 : its density varies from 
2-5 to 2-8. The rarer variety, or arragonite, is found in crystals whose pri- 
mary form is a right rhombic prism ; a figure having no geometrical relation 
to the preceding; it is, besides, heavier and harder. 

Phosphates of lime. — A number of distinct compounds of lime and phos- 
phoric acid probably exist. Two tribasic phosphates, 2CaO,HO,P0 5 , and 
•3CaOP0 5 , are produced when the corresponding soda-salts are added in so- 
lution to chloride of calcium ; the first is slightly crystalline, and the second 
gelatinous. When the first phosphate is digested with ammonia, or dissolved 
in acid and re-precipitated by that alkali, it is converted into the second. 

1 Many proposals have been made to prevent the formation of boiler-deposits. The most 
efficient appears to be the method of Dr. Kitterband, which consists in throwing into the 
boiler a small quantity of sal-ammoniac, when carbonate of ammonia is formed, which is 
volatilized with the steam, chioride of calcium remaining in solution. It need scarcely be 
mentioned that this plan is inapplicable in the case of permanently bard waters. 



CALCIUM. 243 

fae earth of bones consists principally of what appears to be a combi- 
nation of these two salts. Another phosphate, containing 2 equivalents 
of basic water, has been described, which completes the series ; it is formed 
by dissolving either of the preceding in phosphoric, hydrochloric, or nitric 
acid, and evaporating until the salt separates on cooling in small platy crys- 
tals. It is this substance which yields phosphorus, when heated with char- 
coal, in the ordinary process of manufacture before described. Bibasic and 
monobasic phosphates of lime also exist. These phosphates, although inso- 
luble in water, dissolve readily in dilute acids, even acetic acid. 

Fluoride of calcium ; fluor-spar ; CaF. — This substance is important 
as the most abundant natural source of hydrofluoric acid and the other 
fluorides. It occurs beautifully crystallized, in various colours, in lead-veins, 
the crystals having commonly the cubic, but sometimes the octahedral form, 
parallel to the faces of which latter figure they always cleave. Some varie- 
ties, when heated, emit a greenish phosphorescent light. The fluoride is 
quite insoluble in water, and is decomposed by oil of vitriol in the manner 
already mentined, vide p. 149. 

Chloride of lime ; bleaching-powder. — When hydrate of lime, very 
slightly moist, is exposed to chlorine gas, the latter is eagerly absorbed, and 
a compound produced which has attracted a great deal of attention ; this is 
the bleaching-powder of commerce, now manufactured on an immense scale, 
for bleaching linen and cotton goods. It is requisite, in preparing this sub- 
stance, to avoid with the greatest care all elevation of temperature, which 
may be easily done by slowly supplying the chlorine in the first instance. 
The product, when freshly and well prepared, is a soft, white powder, which 
attracts moisture from the air, and exhales an odour sensibly different from 
that of chlorine. It is soluble in about 10 parts of water, the unaltered hy- 
drate being left behind ; the solution is highly alkaline, and bleaches feebly. 
When hydrate of lime is suspended in cold water, and chlorine gas trans- 
mitted through the mixture, the lime is gradually dissolved, and the same 
peculiar bleaching compound produced ; the alkalis also, either caustic or 
carbonated, may by similar means be made to absorb a large quantity of 
chlorine, and give rise to corresponding compounds ; such are the " disinfect- 
ing solutions" of M. Labarraque. 

The most consistent view of the constitution of these curious compounds 
is that which supposes them to contain salts of hypochlorous acid, a substance 
as remarkable for bleaching powers as chlorine itself; and this opinion seems 
borne out by a careful comparison of the properties of the bleaching-salts 
with those of the true hypochlorites. Hypochlorous acid can be actually ob- 
tained from good bleaching-powder, by distilling it with dilute sulphuric or 
nitric acid, in quantity insufficient to decompose the whole ; when the acid is 
used in excess, chlorine is disengaged. 1 

If this view be correct, chloride of calcium must be formed simultaneously 
with the hypochlorite, as in the following diagram: — 

Chlorine _^ Chloride of calcium. 

\ Calcium 
Chlorine 
Lime " '^--""'^ 'Hypochlorite of lime. 

When the temperature of the hydrate of lime has risen during the absorption 
of the chlorine, or when the compound has been subsequently exposed to 
heat, its bleaching properties are impaired or altogether destroyed ; it then 
contains chlorate of lime and chloride of calcium ; oxygen, in variable quan- 

1 M. Gay-Lussac, Ann. China, ct Phys. 3rd series, v. 296 




214 CALCIUM. 

tity, is usually set free. The same change seems to ensue by long keeping, 
even at the common temperature of the air. In an open vessel it is speedily 
destroyed by the carbonic acid of the atmosphere. Commercial bleaching- 
powder thus constantly varies in value "with its age, and with the care origi- 
nally bestowed upon its preparation : the best may contain about 80 per cent, 
of available chlorine, easily liberated by an acid, which is, however, far short 
of the theoretical quantity. 

The general method in which this substance is employed for bleaching is 
the following : — the goods are first immersed in a dilute solution of chloride 
of lime and then transferred to a vat containing dilute sulphuric acid. De- 
composition ensues ; both the lime of the hypochlorite and the calcium of 
the chloride are converted into sulphate of lime, while the free hypochlorous 
and hydrochloric acids yield water and free chlorine. 

The chlorine thus disengaged in contact with the cloth, causes the destruc- 
tion of the colouring matter. This process is often repeated, it being unsafe 
to use strong solutions. White patterns are on this principle imprinted upon 
coloured cloth, the figures being stamped with tartaric acid thickened with 
gum-water, and then the stuff immersed in the chloride bath, when the 
parts to which no acid has been applied remain unaltered, while the printed 
portions are bleached. 

For purifying an offensive or infectious atmosphere, as an aid to proper 
ventilation, the bleaching-powder is very convenient. The solution is exposed 
in shallow vessels, or cloths steeped in it are suspended in the apartment, 
when the carbonic acid of the air slowly decomposes it in the manner above 
described. An addition of a strong acid causes rapid disengagement of 
chlorine. 

The value of any sample of bleaching-powder may be easily determined by 
the following method, in which the loosely combined chlorine is estimated 
by its effect in peroxidizing a protosalt of iron, of which two equivalents re- 
quire one of chlorine ; the latter acts by decomposing water and liberating 
a corresponding quantity of oxygen — 78 (more correctly 78-16) grains of 
green sulphate of iron are dissolved in about two ounces of water, and acidu- 
lated by a few drops of sulphuric or hydrochloric acid ; this quantity will 
require for peroxidation 10 grains of chlorine. Fifty grains of the chloride 
of lime to be examined are next rubbed up with a little tepid water, and the 
whole transferred to the alkalimeter l before described, which is then filled 
up to with water, after which the contents are well mixed by agitation. 
The liquid is next gradually poured into the solution of iron, with constant 
stirring until the latter has become peroxidized, which may be known by a 
drop ceasing to give a deep blue precipitate with ferricyanide of potassium. 
The number of grain-measures of the chloride solution employed may" then 
be read off, since these must contain 10 grains of serviceable chlorine, the 
quantity of the latter in the 50 grains may be easily reckoned. Thus, sup- 
pose 72 such measures have been taken, then 

Measures. Grs. chlorine. Measures. Grs. chlorine. 

72 : 10 = ' 100 : 13-89 

The bleaching-powder contains, therefore, 27-78 per cent. 3 

Baryta, strontia, and lime are thus distinguished from all other substances, 
and from each other. 

Caustic potassa, when free from carbonate, and caustic ammonia, occasion 
no precipitates in dilute solutions of the earths, especially of the first two, 
the hydrates being soluble in water. 

1 Yid« p. 227. 3 Graham's Elements, vol. i. p. 414. 



MAGNESIUM. 245 

Alkaline carbonates, and carbonate of ammonia, give white precipitates, 
/nsoluble in excess of the precipitant, with all three. 

Sulphuric acid, or a sulphate, added to very dilute solutions of the earths 
in question, gives an immediate white precipitate with baryta, a similar pre- 
cipitate after a short interval with strontia, and occasions no change with 
the lime-salt. The precipitates with baryta and strontia are quite insoluble 
in nitric acid. 

Solution of sulphate of lime gives an instantaneous cloud with baryta, 
and one with strontia after a little time. Sulphate of strontia is itself suffi- 
ciently soluble to occasion turbidity when mixed with chloride of barium. 

Lastly, the soluble oxalates give a white precipitate in the most dilute so- 
lutions of lime, which is not dissolved by a drop or two of hydrochloric nor 
by an excess of acetic acid. This is an exceedingly characteristic test. 

The chlorides of strontium and calcium dissolved in alcohol colour the 
flame of the latter red or purple ; salts of baryta communicate to the flame 
a pale green tint. 

MAGNESIUM. 

A few pellets of sodium are placed at the bottom of a test-tube of hard 
German glass, and covered with fragments of fused chloride of magnesium, 
the heat of a spirit-lamp is then applied until reaction has been induced ; 
this takes place with great violence and elevation of temperature, chloride 
of sodium being formed, and metallic magnesium set free. When the tube 
and its contents are completely cold, it is broken up, and the fragments put 
into cold water, by which the metal is separated from the salt. 

Magnesium is a white, malleable metal, fusible at a red-heat, and not sen- 
sibly acted upon by cold water ; it is oxidized by hot water. Heated in the 
air, it burns and produces magnesia, which is the only oxide. Sulphuric 
and hydrochloric acids dissolve it readily, evolving hydrogen. 

The equivalent of this metal is 12, and its symbol Mg. 

Magnesia ; calcined magnesia ; MgO. — This is prepared with great ease 
by exposing the magnesia alba of pharmacy to a full red-heat in an earthen 
or platinum crucible. It forms a soft, white powder, which slowly attracts 
moisture and carbonic acid from the air, and unites quietly with water to a 
hydrate which possesses a feeble degree of solubility, requiring about 5,000 
parts of water at 60° (15°-5C) and 36,000 parts at 212° (100°C). The al- 
kalinity of magnesia can only be observed by placing a small portion in a 
moistened state upon test-paper ; it neutralizes acids, however, in the most 
complete manner. It is infusible. 

Chloride of magnesium, MgCl. — When magnesia, or its carbonate, is 
dissolved in hydrochloric acid, there can be no doubt respecting the simul- 
taneous production of chloride of magnesium and water ; but when this so- 
lution comes to be evaporated to dryness, the last portions of water are 
retained with such obstinacy, that decomposition of the water is brought 
about by the concurring attractions of magnesium for oxygen, and of chlo- 
rine for hydrogen; hydrochloric acid is expelled, and magnesia remains, 
If, however, sal-ammoniac or chloride of potassium happen to be present, a 
double salt is produced, which is easily rendered anhydrous. The best mode 
of preparing the chloride is to divide a quantity of hydrochloric acid into 
two equal portions, to neutralize one with magnesia, and the other with am- 
monia, or carbonate of ammonia ; to mix these solutions, evaporate them to 
dryness, and then expose the salt to a red-heat in a loosely covered porce- 
lain crucible. Sal-ammoniac sublimes, and chloride of magnesium in a fused 
state remains ; the latter is poured out upon a clean stone, and when cold, 
transferred to a well-stopped bottle. 

The chloride so obtained is white and crystalline. It is very deliquescent 
21* 



246 MAGNESIUM. 

and highly soluble in water, from which it cannot again be recovered by 
evaporation, for the reasons just mentioned. When long exposed to the air 
in a melted state, it is converted into magnesia. It is soluble in alcohol. 

Sulphate of magnesia Epsom salt; MgO,S0 3 -}-7HO. — This salt occurs 
in sea-water, and in that of many mineral springs, and is now manufactured 
in large quantities by acting on magnesian lime-stone by diluted sulphuric 
acid, and separating the sulphate of magnesia from the greater part of the 
slightly soluble sulphate of lime by the filter. The crystals are derived 
from a right rhombic prism ; they are soluble in an equal weight of water 
at 60° (15°-5C), and in a still smaller quantity at 212° (100°C). The salt 
has a nauseous bitter taste, and, like many other neutral salts, purgative 
properties. "When exposed to heat, 6 equivalents of water readily pass off, 
the seventh being energetically retained. Sulphate of magnesia forms beau- 
tiful double salts with the sulphates of potassa and ammonia, which contain 
6 equivalents of water of crystallization. 

Carbonate of magnesia. — The neutral carbonate, MgO,C0 2 , occurs native 
in rhombohedral crystals, resembling those of calcareous spar, embedded in 
talc-slate : a soft earthy variety is sometimes met with. 

When magnesia alba is dissolved in carbonic acid water, and the solution 
left to evaporate spontaneously, small prismatic crystals are deposited, 
which consist of carbonate of magnesia, with 3 equivalents of water. 

The magnesia alba itself, although often called carbonate of magnesia, is 
not so in reality ; it is a compound of carbonate with hydrate. It is pre- 
pared by mixing hot solutions of carbonate of potassa or soda, and sulphate 
of magnesia, the latter being kept in slight excess, boiling the whole a few 
minutes, during which time much carbonic acid is disengaged, and then well 
washing the precipitate so produced. If the solution be very dilute, the 
magnesia alba is exceedingly light and bulky ; if otherwise, it is denser. 
The composition of this precipitate is not perfectly constant. In most cases 
it contains 4(MgO,C0 2 ) -f- MgO,HO + 6IIO. 

Magnesia alba is slightly soluble in water, especially when cold. 

Phosphate of magnesia, 2MgO,HO,P0 5 -|- 14HO. — This salt separates 
in small colourless prismatic crystals when solutions of phosphate of soda 
and sulphate of magnesia are mixed and suffered to stand some time. Prof. 
Graham states that it is soluble in about 1,000 parts of cold water, but 
Berzelius describes a phosphate which only requires 15 parts of water for 
solution : this can hardly be the same substance. Phosphate of magnesia 
exists in the grain of the cereals, and can be detected in considerable 
quantity in beer. 

Phosphate of magnesia and ammonta, 2MgO,NH 4 0,P0 5 -r-12HO. — When 
a soluble phosphate is mixed with a salt of magnesia, and ammonia or its 
carbonate added, a crystalline precipitate, having the above composition, 
subsides immediately, if the solutions are concentrated, and after some time 
if very dilute ; in the latter case, the precipitation is promoted by stirring. 
This salt is slightly soluble in pure water, but scarcely so in saline liquids. 
When heated, it is resolved into bibasic phosphate (pyrophosphate) of mag- 
nesia, containing 35-71 per cent, of magnesia. At a strong red-heat it fuses 
to a white enamel-like mass. The phosphate of magnesia and ammonia 
sometimes forms an urinary calculus. 

In practical analysis, magnesia is often separated from solutions by 
bringing it into this state. The liquid, free from alumina, lime, &c, is 
mixed with phosphate of soda and excess of ammonia, and gently heated 
lor a short time. The precipitate is collected upon a filter and thoroughly 
washed with water containing a little sal-ammoniac, after which it is dried, 
ignited to redness, and weighed. The proportion of magnesia is then easily 
calculated. 



MAGNESIUM. 247 

Silicates of magnesia. — The following natural compounds belong to this 
class: — Steatite or soap-stone, MgO,Si0 3 , a soft, white, or pale-coloured, amor- 
phous substance, found in Cornwall and elsewhere ; Meerschaum, MgO,Si0 3 -L- 
HO, from which pipe-bowls are often manufactured; — Chrysolite, 3MgO,Si0 3 , 
a crystallized mineral, sometimes employed for ornamental purposes ; a \>ov- 
tion of magnesia is commonly replaced by protoxide of iron which communi- 
cates a green colour ; — Serpentine is a combination of silicate and hydrate of 
magnesia ; — Jade, an exceedingly hard stone, brought from New Zealand, con- 
tains silicate of magnesia combined with silicate of alumina ; its green 
colour is due to sesquioxide of chromium; — Augite and hornblende are 
essentially double salts of silicic acid, magnesia, and lime, in which the 
magnesia is more or less replaced by its isomorphous substitute, protoxide 
of iron. 



The salts of magnesia are strictly isomorphous with those of the protox- 
ides of zinc, of iron, of copper, &c. ; they are usually colourless, and are 
easily recognised by the following characters : — 

A gelatinous white precipitate with caustic alkalis, including ammonia, 
insoluble in excess, but soluble in solution of sal-ammoniac. 

A white precipitate with the carbonates of potassa and soda, but none 
with carbonate of ammonia in the cold. 

A white crystalline precipitate with soluble phosphates, on the addition 
of a little ammonia. 



248 ALUMINIUM. 



SECTION III. 
METALS OF THE EARTHS PROPER. 



ALUMINUM OR ALUMINIUM. 



Alumina, the only known oxide of this metal, is a substance of very abun- 
dant occurrence in nature in the state of silicate, as in felspar and its asso- 
ciated minerals, and in the various modifications of clay thence derived. 
Aluminium is prepared in the same manner as magnesium, but with rather 
more difficulty; a platinum or iron tube closed at one extremity may be em- 
ployed. Sesquichloride of aluminium is first introduced, and upon that 
about an equal bulk of potassium loosely wrapped in platinum foil. The 
lower part of the tube is then heated so as to sublime the chloride and brine 
its vapours in contact with the melted potassium. The reduction takes place 
with great disengagement of heat. The metal, separated by cold water from 
the alkaline chloride, has a tin-white colour and perfect lustre. It is ob- 
tained in small fused globules by the heat of reduction, which are malleable, 
and have a specific gravity of 2-6. When heated in the air or in oxygen, it 
takes fire and burns with brilliancy, producing alumina. 

Aluminium has for its equivalent the number 13-7 ; its symbol is Al. 

Alumina, A1 2 3 . — This substance is inferred to be a sesquioxide, from its 
isomorphism with the red oxide of iron. It is prepared by mixing solution 
of alum with excess of ammonia, by which an extremely bulky, white, gela- 
tinous precipitate of hydrate of alumina is thrown down. This is washed, 
dried, and ignited to whiteness. Thus obtained, alumina constitutes a white, 
tasteless, coherent mass, very little acted upon by acids. The hydrate, on 
the contrary, when simply dried in the air, or by gentle heat, dissolves freely 
in dilute acid, and in caustic potassa or soda, from which it is precipitated 
by the addition of sal-ammoniac. Alumina is fusible before the oxyhydro- 
gen blowpipe. The mineral called corundum, of which the ruby and sap- 
phire are transparent varieties, consists of nearly pure alumina in a crystal- 
lized state, with a little colouring oxide ; emery, used for polishing glass and 
metals, is a coarse variety of corundum. Alumina is a very feeble base, 
and its salts have often an acid reaction. 

Sesquichloride of aluminium, A1 2 C1 3 . — The solution of alumina in hydro- 
chloric acid behaves, when evaporated to dryness, like that of magnesia, the 
chloride being decomposed by the water, and alumina and hydi-ochloric acid 
produced. The chloride may be thus prepared: — Pure precipitated alumina 
is dried and mixed with lampblack, and the mixture strongly calcined in a 
covered crucible. It is then transferred to a porcelain tube fixed across a 
furnace, and heated to redness in a stream of chlorine gas, when the alu- 
mina, yielding to the attraction of the chlorine on the one hand, and the 
carbon on the other, for each of its constituents, suffers decomposition, car- 
bonic oxide being disengaged, and sesquichloride of aluminium formed; the 
latter sublimes, and condenses in the cool part of the tube. 



ALUMINIUM. 249 

Sesquichloride of aluminium is a crystalline yellowish substance, exces- 
sively greedy of moisture, and very soluble. Once dissolved, it cannot be 
again recovered. It is said to combine with sulphuretted and phospboretted 
hydrogen, and with ammonia. 

Sulphate of alumina, Al 2 3 ,3S0 3 -{-18HO. — Prepared by saturating 
dilute sulphuric acid with hydrate of alumina, and evaporating. It crystal- 
lizes in thin, pearly plates, soluble in 2 parts of water ; it has a sweet and 
astringent taste, and an acid reaction. Heated to redness, it is decomposed, 
leaving pure alumina. Two other sulphates of alumina, with excess of base, 
are also described, one of which is insoluble in water. 

Sulphate of alumina combines with the sulphates of potassa, soda, and 
ammonia, forming double salts of great interest, the alums. Common alum, 
the source of all the preparations of alumina, contains Al 2 3 ,3S0 3 -f-KO,SO.j 
-j-24110. It is manufactured, on a very large scale, from a kind of slaty clay, 
loaded with bisulphide of iron, which abounds in certain parts. This is 
gently roasted, and then exposed to the air in a moistened state ; oxygen is 
absorbed, the sulphur becomes acidified, sulphate of protoxide of iron and 
sulphate of alumina are produced, and afterwards separated by lixiviation 
with water. The solution is next concentrated, and mixed with a quantity 
of chloride of potassium, which decomposes the iron-salt, forming proto- 
chloride of iron and sulphate of potassa, which latter combines, with the 
sulphate of alumina, to alum. By crystallization, the alum is separated 
from the highly soluble chloride of iron, and afterwards easily purified by a 
repetition of that process. Other methods of alum-making exist, and are 
sometimes employed. Potassa-alum crystallizes in colourless, transparent 
octahedrons, which often exhibit the faces of the cube. It has a sweetish 
and astringent taste, reddens litmus paper, and dissolves in 18 parts of water 
at 60° (15° -5C), and in its own weight of boiling water. Exposed to heat, 
it is easily rendered anhydrous, and, by a very high temperature, decom- 
posed. The crystals have little tendency to change in the air. Alum is 
largely used in the arts, in preparing skins, dyeing, &c. ; it is occasionally 
contaminated with oxide of iron, which interferes with some of its applica- 
tions. The celebrated Roman alum, made from alum-stone, a felspathic rock, 
altered by sulphurous vapours, was once much prized on account of its free- 
dom from this impurity. 

A mixture of dried alum and sugar, carbonized in an open pan, and then 
heated to redness, out of contact of air, furnishes ih.Qpyroph.orus of Homberg, 
which ignites spontaneously on exposure to the atmosphere. The essential 
ingredient is, in all probability, finely divided sulphide of potassium. 

Soda-alum, in which sulphate of soda replaces sulphate of potassa, has a 
form and constitution similar to that of the salt described ; it is, however, 
much more soluble, and difficult to crystallize. 

Ammonia-alum, containing NH 4 0,S0 3 , instead of KO,S0 3 , very closely re- 
sembles common potassa-alum, having the same figure, and appearance, and 
constitution, and nearly the same degree of solubility as that substance. It 
is sometimes manufactured for commercial use. When heated to redness, it 
yields pure alumina. 

Few of the other salts of alumina, except the silicates, present points of 
interest; these latter are "of great importance. Silicates of alumina entei 
into the composition of a number of crystallized minerals, among which 
felspar occupies, by reason of its abundant occurrence, a prominent place 
Granite, porphyry, trachyte, and other ancient unstratified rocks, consist in 
great part of this mineral, which, under peculiar circumstances, by no means 
well understood, and particularly by the action of the carbonic acid of the 
air, suffers complete decomposition, becoming converted into a soft, friable 
mass of earthy matter. This is the origin of clay ; the change itself is seen 



250 BERYLLIUM. 

in great perfection in certain districts of Devonshire and Cornwall, the felspar 
of the fine white granite of those localities being often disintegrated to an 
extraordinary depth, and the rock altered to a substance resembling soft 
mortar. By washing, this finely divided matter is separated from the quartz 
and mica, and the milk -like liquid, being collected in tanks and suffered to 
stand, deposits the suspended clay, which is afterwards dried, first in the 
air and afterwards in a stove, and employed in the manufacture of porcelain. 
The composition assigned to unaltered felspar is A1 2 3 , 3Si0 3 -r-KO,Si0 3 , or 
alum, having silicic acid in the place of sulphuric. The exact nature of the 
change by which it passes into porcelain clay is unknown, although it evi- 
dently consists in the abstraction of silica and alkali. 1 

When the decomposing rock contains oxide of iron, the clay produced is 
coloured. The different varieties of shale and slate result from the alteration 
of ancient clay -beds, apparently in many instances by the infiltration of water 
holding silica in solution; the dark appearance of some of these deposits is 
due to bituminous matter. 

It is a common mistake to confound clay with alumina ; all clays are es- 
sentially silicates of that base ; they often vary a good deal in composition. 
Dilute acids exert little action on these compounds ; but by boiling with oil 
of vitriol, alumina is dissolved out, and finely divided silica left behind. 
Clays containing an admixture of carbonate of lime are termed marls, and 
are recognized by effervescing with acids. 

A basic silicate of alumina, 2A1 2 3 , Si0 3 , is found crystallized, constituting 
the beautiful mineral called cyanite. The compounds formed by the union 
of the silicates of alumina with other, silicates are almost innumerable ; a 
soda-felspar, albite, containing that alkali in place of potassa, is known, and 
there are two somewhat similar lithia-compounds spodumene and petalite. 
The zeolites belong to this class: analcime, nepheline, mesotype, &c, are double 
silicates of soda and alumina, with water of crystallization. Stilbite, heulan- 
dite, laumonite, prehnite, &c, consist of silicate of lime, combined with silicate 
of alumina. The garnets, axinite, mica, &c, have a similar composition, but 
are anhydrous. Sesquioxide of iron is very often substituted for alumina 
in these minerals. 



Alumina, when in solution, is distinguished without difficulty. 

Caustic potassa and soda occasion white gelatinous precipitates of hydrate 
of alumina, freely soluble in excess of the alkali. 

Ammonia produces a similar precipitate, insoluble in excess of the reagent. 

The alkaline carbonates and carbonate of ammonia precipitate the hydrate, 
with escape of carbonic acid. The precipitates are insoluble in excess. 

BERYLLIUM (GLUCINUM). 

This metal is prepared from the chloride in the same manner as aluminium, 
ft is fusible with great difficulty, not acted upon by cold water and burns 
,vhen heated in the air, producing berylla. 

The equivalent of beryllium is 6-9, and the symbol Be. 

1 A specimen of -white porcelain clay from Dartmoor, Devon, gave the author the following 
result on analysis : — 

Silica 47-20 

Alumina, with trace of iron and manganese 38-80 

Lime 0-24 

Water 1200 

Alkali and loss 1'76 

100-00 



CERIUM, LANTHANIUJI, AND DIDTMIUM 251 

Bertlla, Be 2 3 , is a rare earth found in the emerald, beryl, and euelase, 
from which it may be extracted by a tolerably simple process. It very much 
resembles alumina, but is distinguished from that substance by its solubility, 
when freshly precipitated, in a cold solution of carbonate of ammonia, from 
which it is again thrown down on boiling. The salts of berylla have a sweet 
taste, whence its former name glucina (yXvKvs)- 



The metal of a very rare earth, yttria, contained in a few scarce minerals 
The name is derived from Ytterby, a place in Sweden, where one of these, 
gadolinite, is found. It is obtained from the chloride by the process alre&dj 
described ; it resembles in character the preceding metal. 

Ordinary yttria is stated by Professor Mosander to be a mixture of the 
oxides of not less than three metals, namely, Yttrium, erbium, and terbium, 
which differ in the characters of their salts, and in other particulars. The 
first is a very powerful base, the two others are weak ones. They are 
separated with extreme difficulty. 

CERIUM, LANTHANIUM, AND DIDTMIUM. 

The oxides of these very rare metals are found associated in the Swedish 
mineral cerite; the equivalent of cerium is about 47, and its symbol Ce. 
This metal forms a protoxide CeO, and a sesquioxide Ce 2 3 . 

The crude sesquioxide of cerium obtained by precipitating the double 
sulphate of cerium and potassa directly derived from cerite by carbonate of 
potassa, has been shown by Mosander to contain in addition to sesquioxide 
of cerium, the oxides of two other metals, to which the above names were 
given. After ignition it is red-brown. The complete separation of these 
three bodies is attended with the greatest difficulty, and has indeed been 
only partially accomplished. 1 Oxide of cerium may be obtained pure by 
heating the mixture of the three oxides first with diluted and afterwards 
with concentrated nitric acid, which gradually removes the whole of the 
oxides of lathanium and didymium. 

The yellow oxide of cerium, obtained by igniting the nitrate, is a mixture 
of proto- and sesquioxide, which are extremely difficult to obtain in a sepa- 
rate state. The salts of the former are colourless, and are completely pre- 
cipitated by sulphate of potassa; the sulphate of the sesquioxide is yellow, 
and forms a beautiful double salt with sulphate of potassa, which is decom- 
posed by water. The metal cerium has been obtained from the chloride by 
the action of sodium. 

Oxide of lanthanium, as pure as it has been obtained, forms a very pale 
salmon-coloured powder, unchanged by ignition in open or close vessels. In 
contact with water it gives a snow-white bulky hydrate which has an alkaline 
reaction, and decomposes ammoniacal salts by boiling. Its salts are 
crystallizable, colourless, sweet, and astringent, and are precipitated by 
sulphate of potassa. 

A tolerably pure lanthanium-salt may be obtained by slowly crystallizing 
an acid solution containing the sulphates of lanthanium and didymium, 
picking out the rose-coloured crystals (containing didymium), and the viole* 
ones (containing lanthanium and didymium), adding the solution of the latter 
to the mother-liquor, and repeating the process. In this manner the whole 
of the didymium-salt may be finally separated by crystallization. Metallic 
lanthanium is prepared like cerium. 

The occasional brown colour of crude oxide of cerium is due to oxide of 

1 A synopsis of the various methods for the separation of cerium, lanthanium, and didy 
miuni Las been given by Mr. II. Watts. Chem. Soc. Quar. Jour. ii. 140. 



252 ZIRCONIUM — THORIUM — GLASS. 

didymium. In a pure state, it forms a brown powder, soluble in acids, and 
generating a series of red crystallizable salts, from which caustic potassa 
precipitates a violet- blue hydrate, quickly changing by exposure to the air. 
It communicates to glass an amethystine colour. 1 

ZIRCONIUM. 

Prepared by heating the double fluoride of zirconium and potassium with 
potassium, and separating the salt with cold water. The metal is black, 
and acquires a feeble lustre when burnished. It takes fire when heated in 
the air. 

The equivalent of zirconium is 33-6, and its symbol Zr. 

Zirconia, Zr 2 3 , is a rare earth, very closely resembling alumina, found 
together with silica, in the mineral zircon. The salts are colourless and have 
an astringent taste. 

Svanberg has rendered it probable that an undescribed metallic oxide 
exists in certain varieties of zircon, for the metal of which he proposes the 
name of norium. 



The metal of an earth from a very rare mineral, thorite ; it agrees in 
character with aluminium, and is obtained by similar means. 

The equivalent of thorium is 59 -6, and its symbol Th. 

Thoria, ThO, is remarkable for its great specific gravity, and is otherwise 
distinguished by peculiar properties which separate it from all other 
substances. 

Manufacture of Glass, Porcelain, and Earthenware. 

Glass. — Glass is a mixture of various insoluble silicates, with excess of 
silica, altogether destitute of crystalline structure : the simple silicates, formed 
by fusing the bases with silicic acid in equivalent proportions, very often 
crystallize, which happens also with the greater number of the natural sili- 
cates included among the earthly minerals. Compounds identical with some 
of these are also occasionally formed in artificial processses, where large 
masses of melted glassy matter are suffered to cool slowly. The alkaline 
silicates, when in a state of fusion, have the power of dissolving a large 
quantity of silica. 

Two principal varieties of glass are met with in commerce, namely, glass 
composed of silica, alkali, and lime, and glass containing a large proportion 
of silicate of lead ; crown and plate-glass belong to the former division ; flint- 
glass, and the material of artificial gems to the latter. The lead promotes 
fusibility, and confers also density and lustre. Common green bottle glass 
contains no lead, but much silicate of black oxide of iron, derived from the 
impure materials. The principle of the glass manufacture is very simple. 
Silica, in the shape of sand, is heated with carbonate of potassa or soda, 
and slaked lime or oxide of lead; at a high temperature, fusion and combi- 
nation occur, and the carbonic acid is expelled. When the melted mass has 
become perfectly clear and free from air-bubbles, it is left to cool until it as- 
sumes the peculiar tenacious condition proper for working. 

The operation of fusion is conducted in large crucibles of refractory fire- 
clay, which in the case of lead-glass are covered by a dome at the top, and 
have an opening at the side by which the materials are introduced and the 
melted glass withdrawn. Great care is exercised in the choice of the sand, 
which must be quite white and free from oxide of iron. Red-lead, one of 
the higher oxides, is preferred to litharge, although immediately reduced to 

1 Armalen der Cbcmio und Pharmacie, xlviii. 210. 



EARTHENWARE. 255 

The manufacture of porcelain in Europe is of modern origin ; the Chinese 
have possessed the art from the commencement of the seventh century, and 
their ware is, in some respects, altogether unequalled. The materials em- 
ployed by them are known to be kaolin, or decomposed felspar ; petunize, or 
quartz reduced to fine powder ; and the ashes of fern, which contain carbonate 
of potassa. 

Stoneware. — This is a coarse kind of porcelain, made from clay containing 
oxide of iron and a little lime, to which it owes its partial fusibility. The gla- 
zing is performed by throwing common salt into the heated furnace ; this is vo- 
latilized, and decomposed by the joint agency of the silica of the ware, and 
of the vapour of water always present ; hydrochloric acid and soda are pro- 
duced, the latter forming a silicate, which fuses over the surface of the ware, 
and gives a thin, but excellent glaze. 

Earthenware. — The finest kind of earthenware is made from a white 
secondary clay, mixed with a considerable quantity of silica. The articles 
are thoroughly dried and fired, after which they are dipped into a readily 
fusible glaze-mixture, of which oxide of lead is usually an important ingre- 
dient, and, when dry, re-heated to the point of fusion of the latter. The 
whole process is much easier of execution than the making of porcelain, and 
demands less care. The ornamental designs in blue and other colours, so 
common upon plates and household articles, are printed upon paper in enamel 
pigment, mixed with oil, and transferred, while still wet, to the unglazed 
ware. When the ink becomes dry, the paper is washed off, and the glazing 
completed. 

The coarser kinds of earthenware are sometimes covered with a whitish 
opaque glaze, which contains the oxides of lead and tin ; such glaze is very 
liable to be attacked by acids, and is dangerous for culinary vessels. 

Crucibles when of good quality, are very valuable to the practical chemist. 
They are made of clay free from lime, mixed with sand or ground ware of 
the same description. The Hessian and Cornish crucibles are among the 
best. Sometimes a mixture of plumbago and clay is employed for the same 
purpose ; and powdered coke has been also used with the earth ; such cru- 
cibles bear rapid changes of temperature with impunity. 



256 MANGANESE. 



SECTION IV. 

OXIDABLE METALS PROPER, WHOSE OXIDES FORM POWERFUL 

BASES. 



MANGANESE. 

Manganese is tolerably abundant in nature in an oxidized state, forming, 
or entering into the composition of, several interesting minerals. Traces of 
this substance 'are very frequently found in the ashes of plants. 

Metallic manganese, or perhaps, strictly, carbide of manganese, may be 
best prepared by the following process. The carbonate is calcined in an 
open vessel, by which it becomes converted into a dense brown powder ; this 
is intimately mixed with a little charcoal, and about one-tenth of its weight 
of anhydrous borax. A charcoal crucible is next prepared by filling a Hes- 
sian or Cornish crucible with moist charcoal-powder, introduced a little at 
a time, and rammed as hard as possible. A smooth cavity is then scooped 
in the centre, into which the above-mentioned mixture is compressed, and 
covered with charcoal-powder. The lid of the crucible is then fixed, and 
the whole arranged in a very powerful wind-furnace. The heat is slowly 
raised until the crucible becomes red-hot, after which it is urged to its maxi- 
mum for an hour or more. When cold, the crucible is broken up, and the 
metallic button of manganese extracted. 

Manganese is a greyish-white metal, resembling some varieties of cast- 
iron ; it is hard and brittle, and destitute of magnetic properties. Its spe- 
cific gravity is about 8. It is fusible with great difficulty, and, when free 
from iron, oxidizes in the air so readily, that it requires to be preserved in 
naphtha. Water is not sensibly decomposed by manganese in the cold. 
Dilute sulphuric acid dissolves it with great energy, evolving hydrogen. 

The equivalent of manganese is assumed to be 27-6; its symbol is Mn. 

Oxides of Manganese. — Seven different oxides of this metal are described, 
but two out of the number are, probably, secondary compounds. 

Protoxide MnO 

Sesquioxide Mn 2 3 

Binoxide Mn0 2 

Proto-sesquioxide (red oxide) Mn 3 4 =MnO, Mn 2 3 

Varvicite Mn 4 7 =Mn 2 3 2Mn0 2 

Manganic acid Mn0 3 



Pei'manganic acid Mn 2 0, 



Protoxide, MnO. — When carbonate of manganese is heated in a stream 
of hydrogen gas, or of vapour of water, the carbonic acid is disengaged, 
and a green-coloured powder left behind, which is the protoxide. Prepared 
at a dull red-heat only, the protoxide is so prone to absorb oxygen from the 
air, that it cannot be removed from the tube without change ; but when at a 
higher temperature it appears more stable. This oxide is a very powerful 



MANGANESE. 257 

bade, being isomorphous with magnesia and zinc ; it dissolves quietly in 
dilute aoids, neutralizing them completely and forming salts, which have 
often a beautiful pink colour. When alkalis are added to solutions of these 
compounds the white hydrated oxide first precipitated speedily becomes 
brown by passing into a higher state of oxidation. 

Sesquioxide, Mn 2 3 . — This compound occurs in nature in the state of 
hydrate ; a very beautiful crystallized variety is found at Ilefeld, in the 
Hartz. It is produced artificially, by exposing to the air the hydrated prot- 
oxide, and forms the principal part of the residue left in the iron retort when 
oxygen gas is prepared by exposing the native binoxide to a moderate red- 
heat. The colour of the sesquioxide is brown or black, according to its 
origin or mode of preparation. It is a feeble base, isomorphous with alu- 
mina ; for, when gently heated with diluted sulphuric acid, it dissolves to a 
red liquid, which, on the addition of sulphate of potassa or of ammonia, 
deposits octahedral crystals having the constitution of common alum ; these 
are, however, decomposed by water. Strong nitric acid resolves this oxide 
into a mixture of protoxide and binoxide, the former dissolving, and the 
latter remaining unaltered ; while hot oil of vitriol destroys it by forming 
sulphate of the protoxide, and liberating oxygen gas. Heated with hydro- 
chloric acid, chlorine is evolved, as with the binoxide, but to a smaller extent. 

Binoxide, Mn0 2 . — The most common ore of manganese ; it is found both 
massive and crystallized. It may be obtained artificially in the anhydrous 
state by gently calcining the nitrate, or in combination with water, by adding 
solution of bleaching-powder to a salt of the protoxide. Binoxide of man- 
ganese has a black colour, is insoluble in water, and refuses to unite with 
acids. It is decomposed by hot hydrochloric acid and by oil of vitriol in the 
same manner as the sesquioxide. 

As this substance is an article of commerce of considerable importance, 
being used in a very large quantity for making chlorine, and as it is subject 
to great alteration of value from an admixture of the sesquioxide and several 
impurities, it becomes desirable to possess means of assaying different sam- 
ples that may be presented, with a view of testing their fitness for the pur- 
poses of the manufacturer. One of the best and most convenient methods 
is the following : — 50 grains of the mineral, reduced to a very fine powder, 
are put into the little vessel employed in the analysis of carbonates, 1 together 
with about half an ounce of cold water, and 100 grains of strong hydro- 
chloric acid ; 50 grains of crystallixed oxalic acid are then added, the cork 
carrying the chloride of calcium tube is fitted, and the whole quickly 
weighed or counterpoised. The application of a gentle heat suffices to deter- 
mine the action : the disengaged chlorine converts the oxalic acid into car- 
bonic acid, with the help of the elements of water, two equivalents of car- 
bonic acid representing one of chlorine, and consequently one of binoxide 
of manganese. Now, the equivalent of the latter substance, 43-6, is so 
nearly equal to twice that of carbonic acid, 22, that the loss of weight 
suffered by the apparatus when the reaction has has become complete, and 
the residual gas has been driven off by momentary ebullition, may be taken 
to represent the quantity of real binoxide in the 50 grains of the sample 
It is obvious that the little apparatus of Will and Fresenius, described at 
page 229, may be used with the same advantage. 

Ked oxide, Mn 3 4 , or probably MnO-f-Mn 2 3 . — This oxide is also found 
native, and is produced artificially by heating to whiteness the binoxide or 
sesquioxide, or by exposing the protoxide or carbonate to a red-heat in an 
open vessel. It is a reddish-brown substance, incapable of forming salts, 
and acted upon by acids in the same manner as the two higher oxides already 

1 See page 228. 
22* 



258 MANGANESE. 

described. Borax and glass in a fused state dissolve this substance, and 
acquire the colour of the amethyst. 

Varvicite, Mn 4 7 , or Mn 2 3 -j-2Mn0 2 . — A natural production, discovered 
by Mr, Phillips, among certain specimens of manganese-ore from Warwick- 
shire ; it has also been found at Ilefeld. It much resembles the binoxide, 
but is harder and more brilliant, and contains water. By a strong heat, 
varvicite is converted into red oxide, with disengagement of aqueous vapour 
and oxygen gas. 

Chloride op manganese, MnCl. — This salt may be prepared in a state 
of purity from the dark brown liquid residue of the preparation of chlorine 
from binoxide of manganese and hydrochloric acid, which often accumulates 
in the laboratory to a considerable extent in the course of investigation ; 
from the pure chloride, the carbonate and all other salts can be conveniently 
obtained. The liquid referred to consists chiefly of the mixed chlorides of 
manganese and iron ; it is filtered, evaporated to perfect dryness, and then 
slowly heated to dull ignition in an earthen vessel, with constant stirring. 
The chloride of iron is thus either volatilized or converted by the remaining 
water into insoluble sesquioxide, while the manganese-salt is unaffected. On 
treating the greyish-looking powder thus obtained with water, the chloride 
of manganese is dissolved out, and may be separated by filtration from the 
sesquioxide of iron. Should a trace of the latter yet remain, it may be got 
rid of by boiling the liquid for a few minutes with a little carbonate of man- 
ganese. The solution of chloride has usually a delicate pink colour, which 
becomes very manifest when the salt is evaporated to dryness. A strong 
solution deposits rose-coloured tabular crystals, which contain 4 equivalents 
of water ; these are very soluble and deliquescent. The chloride is fusible 
at a red-heat, is decomposed slightly at that temperature by contact of air, 
and is dissolved by alcohol, with which it forms a crystallizable compound. 

Sesquichloride, Mn 2 Cl 3 . — When precipitated sesquioxide of manganese 
is put into cold dilute hydrochloric acid, it dissolves quietly, forming a red 
solution of sesquichloride. Heat disengages chlorine, and occasions the pro- 
duction of protochloride. 

Sulphate of protoxide of manganese, MnO,S0 3 -f-7HO. — A beautiful 
rose-coloured and very soluble salt, isomorphous with sulphate of magnesia. 
It is prepared on a large scale for the use of the dyer, by heating, in a close 
vessel, binoxide of manganese and coal, and dissolving the impure protoxide 
thus obtained in sulphuric acid, with the addition of a little hydrochloric 
acid towards the end of the process. The solution is evaporated to dryness, 
and again exposed to a red-heat, by which the sulphate of sesquioxide of 
iron is decomposed. Water then dissolves out the pure sulphate of manga- 
nese, leaving the sesquioxide of iron behind. The salt is used to produce a 
permanent brown dye, the cloth steeped in the solution being aftewards 
passed through a solution of bleaching-powder, by which the protoxide is 
changed to insoluble hydrate of the binoxide. Sulphate of manganese 
sometimes crystallizes with five equivalents of water. It forms a double salt 
with sulphate of potassa. 

Carbonate of manganese. — Prepared by precipitating the protochloride 
by an alkaline carbonate. It is insoluble and buff-coloured, or sometimes 
nearly white. Exposed to heat, it loses carbonic acid, and absorbs oxygen. 

Manganic acid, Mn0 3 . — When an oxide of manganese is fused with an 
alkali, an additional quantity of oxygen is taken up from the air, and a deep 
green saline mass results, which contains a salt of the new acid, thus formed 
under the influence of the base. The addition of nitre, or chlorate of 
potassa, facilitates the production of manganic acid. Water dissolves this 
compound very readily, and the solution, concentrated by evaporation in 
vacuo, yields green crystals. 



iron. 259 

• Permanganic acid, Mn 2 O r — When manganate of potassa, free from any- 
great excess of alkali, is put into a large quantity of "water, it is resolved 
into hydrated binoxide of manganese, which subsides, and a deep purple 
liquid, containing permanganate of potassa. This effect is accelerated by 
heat. The changes of colour accompanying this decomposition are very re- 
markable, and have procured for the substance the name mineral chameleon ; 
excess of alkali hinders, in some measure, the reaction, by conferring greater 
stability on the manganate. Permanganate of potassa is easily prepared on 
a considerable scale. Equal parts of very finely powdered binoxide of man- 
ganese and chlorate of potassa are mixed with rather more than one pai't of 
hydrate of potassa dissolved in a little water, and the whole exposed, after 
evaporation to dryness, to a temperature just short of ignition. The mass 
is treated with hot water, the insoluble oxide separated by decantation, and 
the deep purple liquid concentrated by heat, until crystals form upon its 
surface ; it is then left to cool. The crystals have a dark purple colour, and 
are not very soluble in cold water. The manganates and permanganates are 
decomposed by contact with organic matter ; the former are said to be iso- 
morphous with the sulphates, and the latter with the perchlorates. 



Salts of the protoxide of manganese are very easily distinguished by 
reagents. 

The fixed caustic alkalis, and ammonia, give white precipitates, insoluble 
in excess, quickly becoming brown. 

The carbonates of the fixed alkalis, and carbonate of ammonia, give white 
precipitates, but little subject to change, and insoluble in excess of carbonate 
of ammonia. 

Sulphuretted hydrogen gives no precipitate, but sulphide of ammonium 
throws down insoluble, flesh-coloured sulphide of manganese, which is very 
characteristic. 

Ferrocyanicle of potassium gives a white precipitate. 

Manganese is also easily detected by the blowpipe ; it gives with borax an 
amethystine bead in the outer or oxidizing flame, and a colourless one in the 
inner flame. Heated upon platinum foil with carbonate of soda, it yields a 
green mass of manganate of soda. 



This is by very far the most important member of the group of metals 
under discussion ; there are few substances to which it yieids in interest, 
when it is considered how very intimately the knowledge of the properties 
and uses of iron is connected with human civilization. 

Metallic iron is of exceedingly rare occurrence ; it has been found at 
Canaan, in Connecticut, 1 forming a vein about two inches thick in mica-slate, 
but it invariably enters into the composition of those extraordinary stones 
known to fall from the air, called meteorites. Isolated masses of soft malleable 
iron also, of large dimensions, lie loose upon the surface of the earth in South 
America and elsewhere, and are presumed to have had a similar origin : 
these latter contain, in common with the iron of the undoubted meteorites, 
nickel. In an oxidized condition, the presence of iron may be said to be 
universal ; it constitutes great part of the common colouring matter of rocks 
and soils ; it is contained in plants, and forms an essential component of the 
blood of the animal body. In the state of bisulphide it is also very common. 
Pure iron may be prepared, according to Mitscherlich, by introducing into 

1 Phillip's Mineralogy, fourth edit. p. 208. 



260 , IRON. 

a Hessian crucible 4 parts of fine iron wire cut small, and 1 part of black • 
oxide of iron. This is covered with a mixture of white sand, lime, and car- 
bonate of potassa, in the proportions used for glass-making, and a cover being 
closely applied, the crucible is exposed to a very high degree of heat. A 
button of pure metal is thus obtained, the traces of carbon and silicum pre- 
sent in the wire having been removed by the oxygen of the oxide. 

Pure iron has a white colour and perfect lustre; it is extremely soft and 
tough, and has a specific gravity of 7-8. The crystalline form is probably 
the cube, to judge from appeai'ances now and then exhibited. In good bai*- 
iron or wire a distinct fibrous texture may always be observed when the 
metal has been attacked by rusting or by the application of an acid, and 
upon the perfection of this fibre much of its strength and value depends. 
Iron is the most tenacious of all the metals, a wire —rth of an inch in diame- 
ter bearing a weight of 601b. It is very difficult of fusion, and before be- 
coming liquid passes through a soft or pasty condition. Pieces of iron 
pressed or hammered together in this state cohere into a single mass ; the 
operation is termed ivelding, and is usually performed by sprinkling a little 
sand over the heated metal, which combines with the superficial film of oxide, 
forming a fusible silicate, which is subsequently forced out from between 
the pieces of iron by the pressure applied ; clean surfaces of metal are thus 
presented to each other, and union takes place without difficulty. 

Iron does not oxidize in dry air at common temperatures ; heated to red- 
ness, it becomes covered with a scaly coating of black oxide, and at a high 
white-heat burns brilliantly, producing the same substance ; in oxygen gas 
the combustion occurs with still greater ease. The finely divided spongy 
metal, prepared by reducing the oxide by hydrogen gas, takes fire spontane- 
ously in the air. 1 Pure water, free from air and carbonic acid, does not 
tarnish a surface of polished iron, but the combined agency of free oxygen 
and moisture speedily leads to the production of rust, which is a hydrate of 
the sesquioxide. The rusting of iron is wonderfully promoted by the pre- 
sence of a little acid vapour. 2 At a red-heat iron decomposes water, evolving 
hydrogen, and passing into the black oxide. Dilute sulphuric and hydro- 
chloric acids dissolve it freely with separation of hydrogen. Iron is strongly 
magnetic up to a red-heat, when it loses all traces of that remarkable pro- 
perty. 

The equivalent of iron is 28, and its symbol Fe. 

Four compounds of iron and oxygen are described. 

Protoxide FeO 

Sesquioxide (peroxide) Fe 2 3 

Protosesquioxide (black oxide) Fe 3 4 =FeO, Fe 2 3 

Ferric acid Fe0 3 

Pbotoxide, FeO. — This is a very powerful base, neutralizing acids com- 
pletely, and isomorphous with magnesia, oxide of zinc, &c. It is almost 
unknown in a separate state, from its extreme proneness to absorb oxygen 
and pass into the sesquioxide. When a salt of this substance is mixed with 
caustic alkali or ammonia, a bulky whitish precipitate of hydrate of the pro- 
toxide falls, which becomes nearly black when boiled, the water being sepa- 

1 When obtained at a heat below redness.— R. B. 

9 The rusting of iron proceeds with rapidity after it once begins, extending from the point 
first affected. Iron rust contains ammonia, resulting from the combination of the nascent 
hydrogen of decomposed water uniting with dissolved nitrogen. This is an important point 
in medico-legal investigations, as it is considered, that, when stains on a steel instrument 
yield ammonia by the action of potassa, the presence of organic matter is proved : but as rust 
nontains ammonia, it becomes necessary to ascertain its absence, or drive it off, previous to 
opfi-anng with potassa. — R. B. 



IRON. 261 

rated. This hydrate exposed to the air, very rapidly changes, becoming 
green and ultimately red-brown. The soluble salts of protoxide of iron have 
commonly a delicate pale green colour, and a nauseous metallic taste. 

Sesquioxide, Fe 2 3 . — A feeble base, isomorphous with alumina. Sesqui- 
oxide of iron occurs native, most beautifully crystallized as specular iron ore 
in the island of Elba, and elsewhere ; also as red and brown hcematites, the 
latter being a hydrate. It is artificially prepared by precipitating a solution 
of sulphate of the sesquioxide or the sesquichloride of iron by excess of am- 
monia, and washing, drying, and igniting the yellowish-brown hydrate thus 
produced ; fixed alkali must not be used in this operation, as a portion is re- 
tained by the oxide. In fine powder, this oxide has a full red colour, and is 
used as a pigment, being prepared for the purpose by calcination of the sul- 
phate of the protoxide ; the tint varies somewhat with the temperature to 
Which it has been exposed. This oxide is unaltered in the fire, although 
easily reduced at a high temperature by carbon or hydrogen. It dissolves 
in acids, with difficulty after strong ignition, forming a series of reddish 
salts, which have an acid reaction and an astringent taste. Sesquioxide of 
iron is not acted upon by the magnet. 1 

Black oxide ; magnetic oxide ; loadstone, Fe 3 4 
Fe 2 3 . — A natural product, one of the most valuable ( 
found in regular octahedral crystals, which are magnetic, ft may be pre- 
pared by mixing due proportions of salts of the protoxide and sesquioxide 
of iron, precipitating them by excess of alkali, and then boiling the mixed 
hydrates, when the latter unite to a black sandy substance, consisting of 
minute crystals of the magnetic oxide. This oxide is the chief product of 
the oxidation of iron at a high temperature in the air and in aqueous vapour. 
It is incapable of forming salts. 

Ferric acid, Fe0 3 . — A very remarkable compound of recent discovery. 
The simplest mode of preparing it is to heat to full redness, for an hour, in 
a covered crucible, a mixture of one part of pure sesquioxide of iron, and 
four parts of dry nitre. The brown, porous, deliquescent mass is treated 
when cold with ice-cold water, by which a deep amethystine red solution of 
ferrate of potassa is obtained. This gradually decomposes even in the cold, 
evolving oxygen gas, and depositing sesquioxide ; by heat the decomposition 
is very rapid. The solution of ferrate of potassa gives no precipitate with 
salts of lime, magnesia, or strontia, but when mixed with one of baryta, a 
deep crimson, insoluble compound falls, which is a ferrate of that base, and 
is very permanent. 

Protochloride of iron, FeCl. — Formed by transmitting dry hydrochloric 
acid gas over red-hot metallic iron, or by dissolving iron in hydrochloric acid. 
The latter solution yields, when duly concentrated, green crystals of the pro- 
tochloride, containing 4 equivalents of water ; they are very soluble and 
deliquescent, and rapidly oxidize in the air. 

Sesquichloride of iron, Fe 2 Cl 3 . — Usually prepared by dissolving sesqui- 
oxide in hydrochloric acid. The solution, evaporated to a syrupy consistence, 
deposits red, hydrated crystals, which are very soluble in water and alcohol. 
It forms double salts with chloride of potassium and sal-ammoniac. When 
evaporated to dryness and strongly heated, much of the chloride is decom- 
posed, yielding sesquioxide and hydrochloric acid ; the remainder sublimes, 
and afterwards condenses in the form of small brilliant red crystals, which 
deliquesce rapidly. The solution of sesquichloride of iron is capable of dis- 
solving a large excess of recently precipitated hydrate of the sesquioxide, by 

1 In the form of hydrate, FenOa+oIIO, as recently precipitated from the persulphate by am- 
monia, it constitutes the antidote for arsenious acid. The affinity for water in this case is not 
strong — the hydrate gradually decomposing even when kept under water, its colour pa>58iiip 
from yellowish brown to red. — R. B. 



262 iron. 

which it acquires a much darker colour. Anhydrous sesquichloride of iron 
is .also produced by the action of chlorine upon the heated metal. 

Protiodide of iron,, Fel. — This is an important medicinal preparation ; 
it is easily made by digesting iodine -with water and metallic iron. The so- 
lution is pale green, and yields, on evaporation, crystals resembling those of 
the chloride, which rapidly oxidize on exposure to air. It is best preserved 
in solution in contact with excess of iron. 1 A sesqui-iodide of iron exists, 
which is yellowish-red and soluble. 

Sulphides of iron. — Several compounds of iron and sulphur are de- 
scribed ; of these the two most important are the following. Protosulphide, 
FeS, is a blackish, brittle substance, attracted by the magnet, formed by 
heating together iron and sulphur. It is dissolved by dilute acids with evo- 
lution of sulphuretted hydrogen gas, and is constantly employed for that 
purpose in the laboratory, being made by projecting into a red-hot crucible 
a mixture of 2£ parts of sulphur and 4 parts of iron filings or borings of 
cast-iron, and excluding the air as much as possible. The same substance 
is formed when a bar of white hot-iron is brought in contact with sulphur. 
The bisulphide of iron, FeS 2 , iron pyrites, is a natural product, occurring in 
rocks of all ages, and evidently formed in many cases by the gradual de- 
oxidation of sulphate of iron by organic matter. It has a brass-yellow 
colour, is very hard, not attracted by the magnet, and not acted upon by 
dilute acids. Exposed to heat, sulphur is expelled, and an intermediate sul- 
phide, analogous probably to the black oxide, is produced. This substance 
also occurs native, under the name of magnetic pyrites. The bisulphide is 
sometimes used in the manufacture of sulphuric acid. 

Compounds of iron with phosphorus, carbon, and silicium exist, but little 
is known respecting them in a definite state. The carbide is contained in 
cast-iron and in steel, to which it communicates ready fusibility ; the silicium- 
compound is also found in cast-iron. Phosphorus is a very hurtful substance 
in bar-iron, as it renders it brittle or cold-short. 

Sulphate of protoxide of iron; green vitriol, FeO,S0 3 -f-7HO. — This 
beautiful and important salt may be obtained by directly dissolving iron in 
dilute sulphuric acid ; it is generally prepared, however, and that on a very 
large scale, by contact of air and moisture with common iron pyrites, which, 
by absorption of oxygen, readily furnishes the substance in question. Heaps 
of this material are exposed to the air until the decomposition is sufficiently 
advanced ; the salt produced is then dissolved out by water, and the solution 
made to crystallize. It forms large green crystals, of the composition above 
stated, which slowly effloresce and oxidize in the air ; it is soluble in about 
twice its weight of cold water. Crystals containing 4, and also 2 equiva- 
lents of water, have been obtained. Sulphate of protoxide of iron forms 
double salts with the sulphates of potassa and ammonia. 

Sulphate of sesquioxide of iron, Fe 2 3 ,3S0 3 . — Prepared by adding to 
a solution of the protosalt exactly one-half as much sulphuric acid as it 
already contains, raising the liquid to the boiling-point, and then dropping 
in nitric acid until the solution ceases to blacken by such addition. The red 
liquid thus obtained furnishes, on evaporation to dryness, a buff-coloured 
amorphous mass, which, when put into water, very slowly dissolves. "With 
the sulphates of potassa and ammonia, this salt yields compounds having 
the form and constitution of the alums; the crystals are nearly destitute of 
colour. These latter are decomposed by water, and sometimes by long keep- 
ing when in a dry state. They are best prepared by exposing to spontaneous 
evaporation a solution of sulphate of sesquioxide of iron to which sulphate 
of potassa or of ammonia has been added. 

1 Or protected from the action of oxygen by pure honey, or other saccharine substance, 
iu the proportion of one part to three of the solution. — R. B. 



GLASS. 



253 



protoxide by the heat, the liberated oxygen serving to destroy any combus- 
tible matter which might accidentally find its way into the crucible and stain 
the glass by reducing a portion of the lead. Potassa gives a better glass 
than soda, although the latter is very generally employed, from its lower 
price. A certain proportion of broken and waste glass of the same kind is 
always added to the other materials. 

Articles of blown glass are thus made : — The workman begins by collect- 
ing a proper quantity of soft, pasty glass at the end of his blow-pipe, an 
iron tube, five or six feet in length, terminated by a mouth-piece of wood ; 
he then commences blowing, by which the lump is expanded into a kind of 
flask, susceptible of having its form modified by the position in which it is 
held, and the velocity of rotation continually given to the iron tube. If an 
open-mouthed vessel is to be made, an iron rod, called a pontil or puntil, is 
dipped into the glass-pot and applied to the bottom of the flask, to which it 
thus serves as a handle, the blowpipe being removed by the application of a 
cold iron to the neck. The vessel is then re-heated at a hole left for the 
purpose in the wall of the furnace, and the aperture enlarged, and the vessel 
otherwise altered in figure by the aid of a few simple tools, until completed. 
It is then detached, and carried to the annealing oven, where it undergoes 
slow and gradual cooling during many hours, the object of which is to obvi- 
ate the excessive brittleness always exhibited by glass which has been 
quickly cooled. The large circular tables of crown-glass are made by a very 
curious process of this kind ; the globular flask at first produced, trans- 
ferred from the blowpipe to the pontil, is suddenly made to assume the form 
of a flat disc by the centrifugal force of the rapid rotatory movement given 
to the rod. Plate-glass is cast upon a flat metal table, and after very care- 
ful annealing, ground true and polished by suitable machinery. Tubes are 
made by rapidly drawing out a hollow cylinder ; and from these a great va- 
riety of useful apparatus may be constructed with the help of a lamp and 
blowpipe, or still better, the bellows-table of the barometer-maker. Small 
tubes may be bent in the flame of a spirit-lamp or gas-jet, and cut with 
great ease by a file, a scratch being made, and the two portions pulled or 
broken asunder in a way easily learned by a few trials. 

Specimens of the two chief varieties of glass gave the following results 
on analysis : — 



Bohemian plate-glass (excellent). 1 

Silica 60-0 

Potassa 25-0 

Lime 12-5 

97-5 



English flint-glass. 3 

Silica 51-93 

Potassa 13-77 

Oxide of lead 33-28 



■98 



The difficultly-fusible white Bohemian tube, so invaluable in organic che- 
mistry, has been found to contain in 100 parts : — 

Silica 72-80 

Lime, with trace of alumina 9-68 

« Magnesia -40 

Potassa 16-80 

Traces of manganese, &c, and loss -32 

Different colours are often communicated to glass by metallic oxides. 
Thus, oxide of cobalt gives deep blue ; oxide of manganese, amethyst ; sub- 
oxide of copper, ruby-red; black oxide of copper, green; the oxides of 
iron, dull green or brown, &c. These are either added to the melted con 

1 Mitscherlich, Lehrbuch, ii. 187 a Faraday. 

22 



254 PORCELAIN AND EARTHENWARE. 

tents of the glass-pot, in which they dissolve, or applied in a particular 
manner to the surface of the plate or other object, which is then re-heated 
until fusion of the colouring matter occurs ; such is the practice of enam- 
elling and glass-painting. An opaque white appearance is given by oxide 
of tin ; the enamel of watch-faces is thus prepared. 

When silica is melted with twice its weight of carbonate of potassa or 
soda, and the product treated with water, the greater part dissolves, yielding 
a solution from which acids precipitate gelatinous silica. This is the soluble 
glass sometimes mentioned by chemical writers ; its solution has been used 
for rendering muslin and other fabrics of cotton or linen less combustible. 

Porcelain and earthenware. — The plasticity of natural clays, and their 
hardening when exposed to heat, are properties which suggested in very early 
times their application to the making of vessels for the various purposes of 
daily life ; there are few branches of industry of higher antiquity than that 
exercised by the potter. 

True porcelain is distinguished from earthenware by very obvious charac- 
ters. In porcelain the body of the ware is very compact and translucent, 
and breaks with a conchoidal fracture, symptomatic of a commencement of 
fusion. The glaze, too, applied for giving a perfectly smooth surface, is 
closely adherent, and in fact graduates by insensible degrees into the sub- 
stance of the body. In earthenware, on the contrary, the fracture is open 
and earthy, and the glaze detachable with greater or less facility. The com- 
pact and partly glassy character of porcelain is the result of the admixture 
with the clay of a small portion of some substance, fusible at the temperature 
to which the ware is exposed when baked or fired, and which, absorbed by 
the more infusible portion, binds the whole into a solid mass on cooling ; 
such substances are found in felspar, and in a small admixture of silicate 
of lime, or alkali. The clay employed in porcelain-making is always 
directly derived from the decomposed felspar, none of the clays of the secon- 
dary strata being pure enough for the purpose ; it must be white, and free 
from oxide of iron. To diminish the retraction which this substance under- 
goes in the fire, a qantity of finely divided silica, carefully prepared by 
crushing and grinding calcined flints or chert, is added, together with a 
proper proportion of felspar or other fusible material, also reduced to impal- 
pable powder. The utmost pains are taken to effect perfect uniformity of 
mixture, and to avoid the introduction of particles of grit or other foreign 
bodies. The ware itself is fashioned either on the potter's wheel ; — a kind 
of vertical lathe; — or in moulds of plaster of Paris, and dried, first in the air, 
afterwards by artificial heat, and at length completely hardened by exposure 
to the temperature of ignition. The porous biscuit is now fit to receive its 
glaze, which may be either ground felspar, or a mixture of gypsum, silica, 
and a little porcelain clay, diffused through water. The piece is dipped for 
a moment into this mixture, and withdrawn ; the water sinks into its sub- 
stance, and the powder remains evenly spread upon its surface ; it is once 
more dried, and lastly, fired at an exceedingly high temperature. 

The porcelain-furnace is a circular structure of masonry, having several 
fire-places, and surmounted by a lofty dome. Dry wood or coal is consumed 
as fuel, and its flame directed into the interior, and made to circulate aroilnd 
and among the earthen cases, or seggars in which the articles to be fired are 
packed. Many hours are required for this operation, which must be very 
carefully managed. After the lapse of several days, when the furnace has 
completely cooled, the contents are removed in a finished state, so far as 
regards the ware. 

The ornamental part, consisting of gilding and painting in enamel, has yet 
to be executed, after which the pieces are again heated, in order to flux the 
colours This operation has sometimes to be repeated more than once. 



iron. 263 

Nitrate of the protoxide of iron, FeO,N0 5 . — When dilute cold nitric 
acid is made to act to saturation upon protosulphide of iron, and the solu- 
tion evaporated in vacuo, pale green and very soluble crystals of protonitrate 
are obtained, -which are very subject to alteration. The nitrate of the ses- 
quioxide is readily formed by pouring nitric acid, slightly diluted, upon iron ; 
it is a deep red liquid, apt to deposit an insoluble basic salt, and is used in 
dyeing. 

Carbonate of protoxide of iron, FeO,C0 2 . — The white precipitate ob- 
tained by mixing solutions of protosalt of iron and alkaline carbonate ; it 
cannot be washed and dried without losing carbonic acid and absorbing 
oxygen. This substance occurs in nature as spathose iron ore, associated with 
variable quantities of carbonate of lime and of magnesia ; and also in the 
common clay iron-stone, from which nearly all the British iron is made. It 
is often found in mineral waters, being soluble in excess of carbonic acid ; 
such waters are known by the rusty matter they deposit. No carbonate of 
the sesquioxide is known. 

The phosphates of iron are all insoluble. 1 , 



Salts of the protoxide of iron are thus distinguished : — 

Caustic alkalis, and ammonia, give nearly white precipitates, insoluble in 
excess of the reagent, rapidly becoming green, and ultimately brown, by ex- 
posure to air. 

Alkaline carbonates, and carbonate of ammonia, throw down the white 
carbonate, also very subject to change. 

Sulphuretted hydrogen gives no precipitate, but sulphide of ammonium 
throws down black protosulphide of iron, soluble in dilute acids. 

Ferrocyanide of potassium gives a nearly white precipitate, becoming deep 
blue on exposure to air. 

Salts of the sesquioxide are thus characterized : — 

Caustic alkalis, and ammonia, give foxy-red precipitates of hydrated ses- 
quioxide, insoluble in excess. 

The carbonates behave in a similar manner, the carbonic acid escaping. 

Sulphuretted hydrogen gives a nearly white precipitate of sulphur, and 
reduces the sesquioxide to protoxide. 

Sulphide of ammonium gives a black precipitate, slightly soluble in excess. 

Ferrocyanide of potassium yields Prussian blue. 

Tincture or infusion of gall-nuts strikes intense bluish-black with th<3 
most dilute solutions of salts of sesquioxide of iron. 



Iron Manufacture. — This most important branch of industry consists, ad 
now conducted, of two distinct parts ; viz., the production from the ore of a 
fusible (carbide) of iron, and the subsequent decomposition of the carbide, 
and its conversion into pure or malleable iron. 

The clay iron ore is found in association with coal, forming thin beds or 
nodules ; it consists, as already mentioned, of carbonate of iron mixed with 
clay ; sometimes lime and magnesia are also present. It is broken in pieces, 

1 Phosphate of protoxide of Iron, 2FeO, HO.PO5, is formed when a solution of common 
phosphate of soda is added to a solution of protosulphate of iron. It falls as a white preci- 
pitate, gradually becoming bluish by the action of the air; it is soluble in acids, from which 
ammonia again precipitates it, and re-dissolves the precipitate when added in excess. The 
blue phosphate contains perphosphate. 

Phosphate of sesquioxide of Iron is formed by adding common phosphate of soda to per- 
sulphate or perchloride of iron; a white precipitate is produced insoluble in ammonia unless 
an excess of phosphate of soda be present. Digested with the fixe<3 alkalis or ammonia ft 
becomes brown. — K. B. 



264 



IRON. 



and exposed to heat in a furnace resembling a lime-kiln, by which the water 
and carbonic acid are expelled, and the ore rendered dark-coloured, denser, 
and also magnetic ; it is then ready for reduction. The furnace in which 
this operation is performed is usually of very large dimensions, fifty feet or 
more in height, and constructed of brick work with great solidity, the 
interior being lined with excellent fire-bricks ; the figure will be at once 
understood from the sectional drawing (fig. 149). The furnace is close at 




the bottom, the fire being maintained by a powerful artificial blast introduced 
by two or three tuyere-pipes, as shown in the section. The materials, con- 
sisting of due proportions of coke or carbonized coal, roasted ore, and lime- 
stone, are constantly supplied from the top, the operation proceeding con- 
tinuously night and day, often for years, or until the furnace is judged to 
require repair. In the upper part of the furnace, where the temperature is 
still very high, and where combustible gases abound, the iron of the ore is 
probably reduced to the metallic state, being disseminated through the 
earthy matter of the ore; as the whole sinks down and attains a still higher 
degree of heat, the iron becomes converted into carbide by cementation, 
while the silica and alumina unite with the lime, purposely added, to a kind 
of glass or slag, nearly free from oxide of iron. The carbide and slag, both 
in a melted state, reach at last the bottom of the furnace, where they arrange 
themselves in the order of their densities ; the slag flows out at certain 
apertures contrived for the purpose, and the iron is discharged from time to 
time, and suffered to run into rude moulds of sand by opening an orifice at the 



iron. 265 

bottom of the recipient, previously stopped with clay. Such is the origin 
of crude or or cast-iron, of which there are several varieties, distinguished 
by differences of colour, hardness, and composition, and known by the names 
of grey, black, and white iron. The first is for most purposes the best, as it 
admits of being filed and cut with perfect ease. The black and grey kinds 
probably contain a mechanical admixture of graphite, which separates during 
solidification. 

A great improvement has been made in the above described process, by 
substituting raw coal for coke, and blowing hot air, instead of cold, into the 
furnace. This is effected by causing the air, on leaving the blowing-machine, 
to circulate through a system of red-hot iron pipes, until its temperature 
becomes high enough to melt lead. This alteration has already effected a 
prodigious saving in fuel, without, it appears, any injury to the quality of 
the product. 

The conversion of cast into bar-iron is effected by an operation called 
puddling ; previous to which, however, it commonly undergoes a process the 
theory of which is not perfectly intelligible. It is remelted, and suddenly 
cooled, by which it becomes white, crystalline, and exceedingly hard : in this 
state it is called fine-metal. The puddling process is conducted in an ordi- 
nary reverberatory furnace, into which the charge of fine-metal is introduced 
by a side aperture. This is speedily melted by the flame, and its surface 
covered with a crust of oxide. The workman then, by the aid of an iron 
tool, diligently stirs the melted mass, so as intimately to mix the oxide with 
the metal ; he now and then also throws in a little water, with a view of pro- 
moting more rapid oxidation. Small jets of blue flame soon appear upon 
the surface of the iron, and the latter, after a time, begins to lose its fluidity, 
and acquires, in succession, a pasty and a granular condition. At this point, 
the fire is strongly urged, the sandy particles once more cohere, and the 
contents of the furnace now admit of being formed into several large balls 
or masses, which are then withdrawn, and placed und^r an immense hammer, 
moved by machinery, by which each becomes quickly fashioned into a rude 
bar. This is re-heated, and passed between grooved cast-iron rollers, and 
drawn out into a long bar or rod. To make the best iron, the bar is cut into 
a number of pieces, which are afterwards piled or bound together, again 
raised to a welding heat, and hammered or rolled into a single bar ; and this 
process of piling or fagotting is sometimes twice or thrice repeated, the iron 
becoming greatly improved thereby. 

The general nature of the change in the puddling furnace is not difficult 
to explain. Cast-iron consists essentially of iron in combination with carbon 
and silicium ; when strongly heated with oxide of iron, those compounds un- 
dergo decomposition, the carbon and silicium becoming oxidized at the ex- 
pense of the oxygen of the oxide. As this change takes place, the metal 
gradually loses its fusibility, but retains a certain degree of adhesiveness, 
so that when at last it comes under the tilt-hammer, or between the rollers, 
the particles of iron become agglutinated into a solid mass, while the readily 
fusible silicate of the oxide is squeezed out and separated. 

All these processes are, in Great Britain, performed with coal or coke, 
but the iron obtained is, in many respects, inferior to that made in Sweden 
and Russia from the magnetic oxide, by the use of wood charcoal, a fuel too 
dear to be extensively employed in England. Plate-iron is, however, some- 
times made with charcoal. 

Steel.— A very remarkable, and most useful substance, prepared by heat- 
ing iron in contact with charcoal. Bars of Swedish iron are embedded in 
charcoal powder, contained in a large rectangular crucible or chest of some 
substance capable of resisting the fire, and exposed for many hours to a full 
red-heat. The iron takes up, under these circumstances, from 1-3 to 17 
23 



2GG ARIDIUM. 

per cent, of carbon, becoming harder, and at tbe same time fusible, with a 
certain diminution, however, of malleability. The active agent in this ce- 
mentation process is probably carbonic oxide ; the oxygen of the air in the 
crucible combines with the carbon, to form that substance, which is after- 
wards decomposed by the heated iron, one half of its carbon being abstracted 
by the latter. The carbonic acid thus formed takes up an additional dose 
of carbon from the charcoal, and again becomes carbonic oxide, the oxygen, 
or rather the carbonic acid, acting as a carrier between the charcoal and the 
metal. The product of this operation is called blistered steel, from the blis- 
<?red and rough appearance of the bars; the texture is afterwards improved 
ml equalized by welding a number of these bars together, and drawing the 
whole out under a light tilt-hammer. 

The most perfect kind of steel is that which has undergone fusion, having 
been cast into ingot-moulds, and afterwards hammered : of this all fine cut- 
ting instruments are made ; it is difficult to forge, requiring great skill and 
care on the part of the operator. 

Steel may also be made directly from some particular varieties of cast- 
iron, as that from spathose iron ore, containing a little manganese. The 
metal is retained, in a melted state, in the hearth of a furnace, while a 
stream of air plays upon it, and causes partial oxidation ; the oxide pro- 
duced reacts, as before stated, on the carbon of the iron, and withdraws a 
portion of that element. When a proper degree of stiffness or pastiness is 
observed in the residual metal, it is withdrawn, and hammered or rolled into 
bars. The ivootz, or native steel of India, is probably made in this manner. 
Annealed cast-iron, sometimes called run-steel, is now much employed as a 
substitute for the more costly products of the forge ; the articles, when cast, 
are embedded in powdered iron ore, or some earthy material, and, after be- 
ing exposed to a moderate red-heat for some time, are allowed slowly to 
cool, by which a very extraordinary degree of softness and malleability is 
attained. It is very possible that some little decarbonization may take place 
during this process. 

The most remarkable property of steel is that of becoming exceedingly 
hard when quickly cooled ; when heated to redness, and suddenly quenched 
in cold water, steel, in fact, becomes capable of scratching glass with fa- 
cility ; if re-heated to redness, and once more left to cool slowly, it again 
becomes nearly as soft as ordinary iron, and, between these two conditions, 
any required degree of hardness may be attained. The articles, forged into 
shape, are first hardened in the manner described ; they are then tempered, 
or let down, by exposure to a proper degree of annealing heat, which is often 
judged of by the colour of the thin film of oxide which appears on the 
polished surface. Thus, a temperature of about 430° (221°C), indicated by 
a faint straw-colour, gives the proper temper for razors ; that for scissors, 
pen-knives, &c, will be comprised between 470° (243°C) and 490° (254°C), 
and be attended by a full yellow or brown tint. Swords and watch-springs 
require to be softer and more elastic, and must be heated to 550° (288°C) or 
5<i0 o (293°C), or until the surface becomes deep blue. Attention to these 
coloui-s has now become of less importance, as metal baths are often sub- 
stituted for the open fire in this operation. 



Aril»ium (from "Apvs, Mars, and elSos, appearance) from the resemblance 
of its oxide to oxide of iron. Ulgren considers this as a new metal. He 
found it in the chrome iron from Roros, and in iron ore from Oernstolso. 
There are stir doubts hanging over the existence of this metal. 



CHROMIUM. 267 



CHROMIUM. 

Chromium is found in the state of oxide, in combination with oxide of 
lwn, in some abundance in the Shetland Islands, and elsewhere ; as chro- 
mate of lead, it constitutes a very beautiful mineral, from which it was first 
obtained. The metal itself is got in a half-fused condition by mixing the 
oxide with one-fifth of its weight of charcoal-powder, inclosing the mixtuve 
in a crucible lined with charcoal, and then subjecting it to the very highest 
heat of a powerful furnace. It is hard, greyish-white, and brittle; of 5-9 
specific gravity, and exceedingly difficult of fusion. Chromium is but little 
oxidable, being scarcely attacked by the most powerful acids ; it forms at 
least four compounds with oxygen, corresponding to, and probably ismor- 
phous with, those of iron. 

The equivalent of chromium is 26-8 ; its symbol is Cr. 

Protoxide of chromium, CrO. — When potassa is added to a solution of 
the protochloride of chromium, a brown precipitate 'falls, which speedily 
passes to deep foxy red, with disengagement of hydrogen. The protoxide, 
in the state of the pale greenish hydrate, is perhaps obtained when ammonia 
is substituted for potassa in the preceding experiment. This substance is a 
powerful base, forming pale blue salts, which absorb oxygen with extreme 
avidity. The double sulphate of protoxide of chromium and potassa con- 
tains 6 eq. of water, like the other members of the same group. 

Protosesquioxide of chromium, CrO-J-Cr 2 3 , is the above brownish-red 
precipitate produced by the action of water, upon the protoxide. The de- 
composition is not complete without boiling. This oxide corresponds with 
the magnetic oxide of iron, and is not salifiable. 

Sesquioxide of chromium, Cr 2 3 . — When chromate of mercury, prepared 
by mixing solutions of the nitrate of suboxide of mercury and of chromate 
or bichromate of potassa, is exposed to a red-heat, it is decomposed, pure 
sesquioxide of chromium having a fine green colour, remaining. In this 
state the oxide is, like alumina after ignition, insoluble in acids. From a 
solution of sesquioxide of chromium in potassa or soda, green gelatinous 
hydrated sesquioxide of chromium is separated on standing. When finely 
powdered and dried over sulphuric acid, its formula is Cr 2 3 -f-6HO. A hy- 
drate may also be had by boiling a somewhat dilute solution of bichromate 
of potassa, strongly acidulated by hydrochloric acid, with small successive 
portions of sugar or alcohol ; in the foi-mer case, carbonic acid escapes ; in 
the latter a substance called aldehyde and acetic acid are formed, substances 
with which we shall become acquainted in organic chemistry, and the chromic 
acid of the salt becomes converted into sesquichloride of chromium, the 
colour of the liquid changing from red to deep green. A slight excess of 
ammonia precipitates the hydrate from this solution. It has a pale purplish- 
green colour, which becomes full green on ignition ; an extraordinary shrink- 
ing of volume and sudden incandescence is observed when the hydrate is 
decomposed by heat. Anhydrous sesquioxide in a beautifully crystalline 
condition may be prepared by heating to full redness in an earthen crucible 
bichromate of potassa. One-half of the acid suffers decomposition, oxygen 
being disengaged, and oxide of chromium left. The melted mass is then 
treated with water, which dissolves out neutral chromate of potassa, and 
the oxide is, lastly, washed and dried. Sesquioxide of chromium conimu- 
nieates a fine green tint to glass, and is used in enamel-painting. 

The sesquioxide of chromium is a feeble base, resembling, and isomor- 
phous with, sesquioxide of iron and alumina ; the salts it forms have a green 
or purple colour, and are said to be poisonous. 

The sulphate of sesquioxide of chromium is prepared by dissolving the 
hydrated oxide in dilute sulphuric acid. It unites with the sulphates of po- 



268 CHROMIUM. 

tassa and of ammonia, giving rise to magnificent salts -which crystallize in 
regular octahedrons of a deep claret colour, and possess a constitution re- 
sembling that of common alum, the alumina being replaced by sesquioxide 
of chromium. The finest crystals of chromium-alum are obtained by spon- 
taneous evaporation, the solution being apt to be decomposed by heat. 

Protochloride of chromium, CrCl. — The violet-coloured sesquichloride 
of chromium, contained in a porcelain or glass tube, is heated to redness in 
a current of perfectly dry and pure hydrogen gas ; hydrochloric acid is dis- 
engaged, and a white foliated mass is obtained, which dissolves in water 
with great elevation of temperature, yielding a blue solution, which, by ex- 
posure to the air, absorbs oxygen with extraordinary energy, acquiring a 
deep green colour, and passing into the state of oxychloride of chromium, 
2Cr 2 Cl 3 , Cr 2 3 . The protochloride of chromium is one of the most powerful 
reducing or deoxidizing agents known. 

Sesquichloride or chromium, Cr 2 Cl 3 . — This substance is readily obtained 
in the anhydrous condition by heating to redness in a porcelain tube a mix- 
ture of sesquioxide of chromium and charcoal, and passing dry chlorine gas 
over it. The sesquichloride sublimes, and is deposited in the cool part of 
the tube, in the form of beautiful crystalline plates of a pale violet colour. 
According to M. Peligot, it is totally insoluble in water under ordinary cir- 
cumstances, even at a boiling heat. It dissolves, however, and assumes the 
deep green hydrated state in water containing an exceedingly minute quan- 
tity of the protochloride in solution. The hydration is marked by the evo- 
lution of much heat. This remarkable effect must probably be referred to 
the class of actions known at present under the name of katalysis. 1 



The salts of the sesquioxide of chromium are easily recognized. 

Caustic alkalis precipitate the hydrated oxide, easily soluble in excess. 

Ammonia, the same, but nearly insoluble. 

Carbonates of potassa, soda, and ammonia, throw down a green precipitate 
of carbonate and hydrate, slightly soluble in a large excess. 

Sulphuretted hydrogen causes no change. 

Sulphide of ammonium precipitates the hydrate of the sesquioxide. 

Chromic acid, Cr0 3 . — Whenever sesquioxide of chromium is strongly 
heated with an alkali, in contact with the air, oxygen is absorbed and 
chromic acid generated. Chromic acid may be obtained nearly pure, and in 
a state of great beauty, by the following simple process: — 100 measures of 
a cold saturated solution of bichromate of potassa are mixed with 150 
measures of oil of vitriol, and the whole suffered to cool ; the chromic acid 
crystallizes in brilliant crimson-red prisms. The mother-liquor is poured 
off, and the crystals placed upon a tile to drain, being closely covered by a 
glass or bell-jar. 2 Chromic acid is very deliquescent and soluble in water ; 
the solution is instantly reduced by contact with organic matter. 

CJtromate of Potassa, KO,Cr0 3 . — This is the source of all the preparations 
of chromium ; it is made directly from the native chrome-iron ore, which is a 
compound of the sesquioxide of chromium and protoxide of iron, analogous 
to magnetic iron ore, by calcination with nitre or with carbonate of potassa, 
*he stone being reduced to powder, and heated for a long time with the 
alkali in a reverberatory furnace. Tiie product, when treated with water, 
yields a yellow solution, which by evaporation deposits anhydrous crystals 
of the same colour, isomorphous with sulphate of potassa. Chromate of 
potassa has a cool, bitter, and disagreeable taste, and dissolves in 2 parts of 
water at 60° (15°-5C). 

1 See pa?e 186. 

,J Mr. Warrington; Proceedings of Chem. Soc. i. 18. 



NICKEL. 269 

Bichromate of Potassa, K0,2O0 3 , — When sulphuric acid is added to the 
preceding salt in moderate quantity, one-half of the base is removed, and 
the neutral chromate converted into bichromate. The new salt, of which 
immense quantities are manufactured for use in the arts, crystallizes by slow 
evaporation in beautiful red tabular crystals, derived from an oblique rhombic 
prism. It melts when heated, and is soluble in 10 parts of water, and the 
solution has an acid reaction. 

Chromate of Lead, PbO,Cr0 3 . — On mixing solution of chromate or bichro- 
mate of potassa with nitrate or acetate of lead, a brilliant yellow precipitate 
falls, which is the compound in question; it is the chrome-yellow of the 
painter. When this compound is boiled with liuie-water, one-half of the 
acid is withdrawn, and a subchromate of an orange-red colour left. The 
subchromate is also formed by adding chromate of lead to fused nitre, and 
afterwards dissolving out the soluble salts by water ; the product is crystal- 
line, and rivals vermilion in beauty of tint. The yellow and orange chrome - 
colours are fixed upon cloth by the alternate application' of the two solutions, 
and in the latter case by passing the dyed stuff through a bath of boiling 
lime-water. 

Chromate of Silver, AgO,Cr0 3 ! — This salt precipitates as a reddish brown 
powder when solutions of chromate of potassa and nitrate of silver are 
mixed. It dissolves in hot dilute nitric acid, and separates, on cooling, in 
small ruby-red platy crystals. The chromates of baryta, zinc, and mercury 
are insoluble ; the first two are yellow, the last is brick-red. 

Perchromic Acid is obtained, according to Barreswill, by mixing chromic 
acid with dilute binoxide of hydrogen or bichromate of potassa with a dilute 
but very acid solution of binoxide of barium in hydrochloric acid, when a 
liquid is formed of a blue colour, which is removed from the aqueous 
solution by ether. The composition of this very unstable compound is per- 
haps O 2 r 

A salt of chromic acid is at once "recognised by its behaviour with solu- 
tions of baryta and lead ; and also by its colour and capability cf furnishing, 
by deoxidation, the green sesquioxide of chromium. 



Chlorochkomic acid, Cr0 2 -f-Cl. 1 — 3 parts of bichromate of potassa and 
3.} parts of common salt are intimately mixed and introduced into a small 
glass retort ; 9 parts of oil of vitriol are then added, and heat applied as 
long as dense red vapours arise. The product is a heavy deep red liquid 
resembling bromine ; it is decomposed by water, with production of chromic 
and hydrochloric acids. 

Nickel. 

Nickel is found in tolerable abundance in some of the metal-bearing veins 
of the Hartz mountains, and in a few other localities, chiefly as arsenide, the 
kupfernickel of mineralogists, so called from its yellowish-red colour: the 
word nickel is a term of detraction, having been applied by the old German 
miners to what was looked upon as a kind of false copper ore. 

The artificial, or perhaps rather merely fused, product, called speiss, is 
nearly the same substance, and may be employed as a source of the nickel- 
salts. This metal is found in meteoric iron, as already mentioned. 

Nickel is easily prepared by exposing the oxalate to a high white heat, m 

1 If this formula be trebled, we obtain Cr 3 06Cl3 = 2CrO:^CrCl3, and the substance becomes a 
compound of 2 eq. of chromic acid and 1 eq. of terchloride of chromium. The terchlorjde of 
chromium is not known in the free state. 
23* 



270 



NICKEL 



a crucible lined with charcoal. It is a white, malleable metal, having a den- 
sity of 8-8, a high melting point, and a less degree of oxidability than iron, 
since it is but little attacked by dilute acids. Nickel is strongly magnetic, 
but loses this property when heated to 660° (349°C). This metal forms two 
oxides, only one of which is basic. The equivalent of nickel is 29-6 ; its 
symbol is Ni. 

Protoxide of nickel, NiO. — This compound is prepared by heating to 
redness the nitrate, or by precipitating a soluble salt with caustic potassa, 
and washing, drying, and igniting the apple-green hydrated oxide thrown 
down. It is an ash-grey powder, freely soluble in acids, which it completely 
neutralizes, being isomorphous with magnesia, and the other members of the 
same group. The salts of this substance, when hydrated, have usually a 
beautiful green colour; in the anhydrous state they are yellow. 

Sesquioxide, or peroxide of nickel, Ni 2 3 . — This oxide is a black in- 
soluble substance, prepared by passing chlorine through the hydrated oxide 
suspended in water; chloride of nickel is formed, and the oxygen of the 
oxide decomposed transferred to a second portion. It is also produced when 
a salt of nickel is mixed with a solution of bleaching-powder. The sesqui- 
oxide is decomposed by heat, and evolves chlorine when put into hot hydro- 
chloric acid. 

Chloride of nickel, NiCl. — This is easily prepared by dissolving oxide 
or carbonate of nickel in hydrochloric acid. A green solution is obtained 
which furnishes crystals of the same colour, containing water. When ren- 
dered anhydrous by heat, the chloride is yellow, unless it contain cobalt, in 
which case it has a tint of green. 

Sulphate of nickel, NiO,S0 3 -(-7HO. — This is the most important of the 
salts of nickel. It forms green prismatic crystals, containing 7 equivalents 
of water, which require 3 parts of cold water for solution. Crystals with G 
equivalents of water have also been obtained. It forms with the sulphates 
of potassa and ammonia beautiful double salts, NiO,S0 3 -f- KO,S0 3 -f- 6HO 
and J\ T iO,S0 3 -f- NH 4 0, S0 3 -J-6HO. "When a strong solution of oxalic acid 
is mixed with sulphate of nickel, a pale bluish-green precipitate of oxalate 
falls after some time, very little nickel remaining in solution. The oxalate 
can thus be obtained for preparing the metal. 

Carbonate of nickel. — When solutions of sulphate or chloride of nickel 
and of carbonate of soda are mixed, a pale green precipitate falls, which is 
a combination of carbonate and hydrate of nickel. It is readily decomposed 
by heat. 

Pui'e salts of nickel are conveniently prepared on the small scale from 
crude speiss or kupfernickel by the following process: — The mineral is 
broken into small fragments, mixed with from one-fourth to half its weight 
of iron-filings, and the whole dissolved in aqua regia. The solution is gently 
evaporated to dryness, the residue treated with boiling water, and the inso- 
luble arsenate of iron removed by a filter. The liquid is then acidulated 
with hydrochloric acid, treated with sulphuretted hydrogen in excess, which 
precipitates the copper, and, after filtration, boiled with a little nitric acid to 
bring back the iron to the state of sesquioxide. To the cold and largely 
diluted liquid, solution of bicarbonate of soda is gradually added, by which 
the sesquioxide of iron may be completely separated without loss of nickel- 
salt. Lastly, the filtered solution, boiled with cai-bonate of soda in excess, 
yields an abundant pale green precipitate of carbonate of nickel, 1 from which 
all the other compounds may be prepared. 

1 This precipitate may still contain cobalt, which can only be separated from it by very 
complicated processes, for which the more advanced student is referred to "Liebig and K&pp'a 
Annual Report," ii. 334. 



COBALT. 271 

The salts of nickel are well characterized by their behaviour with re- 
agents. 

Caustic alkalis give a pale apple-green precipitate of hydrate, insoluble in 
excess. 

Ammonia affords a similar precipitate, which is soluble in excess, with 
deep purplish-blue colour. 

Carbonate of potassa and soda give pale green precipitates. 

Carbonate of ammonia, a similar precipitate, soluble in excess, with blue 
colour. 

Ferrocyanide of potassium gives a greenish-white precipitate. 

Cyanide of potassium produces a green precipitate, which dissolves in an 
excess of the precipitant to an amber-coloured liquid which is re-precipitated 
hy addition of hydrochloric acid. 

Sulphuretted hydrogen occasions no change, if the nickel be in combina- 
tion with a strong acid. , 

Sulphide of ammonium throws down black sulphide of nickel. 



The chief use of nickel in the arts is in the preparation of a white alloy, 
sometimes called German silver, made by melting together 100 parts of 
copper, 60 of zinc, and 40 of nickel. This alloy is very malleable, and takes 
a high polish. 

COBALT. 

This substance bears, in many respects, an extraordinary resemblance to 
the metal last described ; it is often associated with it in nature, and may 
be obtained from its compounds by similar means. Cobalt is a white, brittle 
metal, having a specific gravity of 8-5, and a vei-y high melting point. It 
is unchanged in the air, and but feebly attacked by dilute hodrochloria 
and sulphuric acids. It is strongly magnetic. There are two oxides of 
this metal, corresponding in properties and constitution with those of 
nickel. 

The equivalent of cobalt is 29-55 : its symbol is Co. 

Protoxide of cobalt, CoO. — This is a grey powder, very soluble in acids, 
and is a strong base, isomorphous with magnesia, affording salts of a fine 
red tint. It is prepared by precipitating sulphate or chloride of cobalt with 
carbonate of soda, and washing and drying and igniting the precipitate. 
AVhen the cobalt-solution is mixed with caustic potassa a beautiful blue pre 
cipitate falls, which when heated becomes violet, and at length dirty red, 
from absorption of oxygen and a change in the state of hydration. 

Sesquioxide of cobalt, Co 2 3 . — The sesquioxide is a black, insoluble, 
neutral powder, obtained by mixing solutions of cobalt and of chloride of 
lime. 

Chloride of cobalt, CoCI. — The chloride is easily prepared by dissolving 
the oxide in hydrochloric acid ; it gives a deep rose-red solution, which, 
when sufficiently strong, deposits hydrated crystals of the same colour. 
When the liquid is evaporated by heat to a very small bulk, it deposits anhy- 
drous crystals which are blue ; these latter by contact with Avater again 
dissolve to a red liquid. A dilute solution of chloride of cobalt constitutes 
the well-known blue sympathetic ink ; characters written on paper with this 
liquid are invisible from their paleness of colour until the salt has been 
rendered anhydrous by exposure to heat, when the letters appear blue. 
"When laid aside, moisture is absorbed, and the writing once more dis- 
appears. Green sympathetic ink is a mixture of the chlorides of cobalt and 
wickel. 



272 zinc. 

Chloride of cobalt may be prepared directly from cobalt-glance, the native 
arsenide, by a process exactly similar to that described in the case of nickel. 

Sulphate of cobalt, CoO,S0 3 -J-7HO. — This salt forms deep red crystals, 
requiring for solution 24 parts of cold water; they are identical in form 
with those of sulphate of magnesia. It combines with the sulphates of po- 
tassa and ammonia, forming double salts, which contain as usual six equiva- 
lents of water. 

A solution of oxalic acid added to one of sulphate of cobalt occasions, 
after some time, the separation of nearly the whole of the base in the state 
of oxalate. 

Carbonate of cobalt. — The alkaline carbonates produce in solution of 
cobalt a pale peach-blossom coloured precipitate of combined carbonate and 
hydrate, containing 3(CoO,HO)-f 2(CoOC0 2 ). 



The salts of cobalt have the following characters: — 

Solution of potassa gives a blue precipitate, changing by heat to violet 
and red. 

Ammonia gives a blue precipitate, soluble with difficulty in excess, with 
brownish red colour. 

Carbonate of soda affords a pink precipitate. 

Carbonate of ammonia, a similar compound, soluble in excess. 

Ferrocyanide of potassium gives a greyish-green precipitate. 

Cyanide of potassium affords a yellowish-brown precipitate, which dissolves 
in an excess of the precipitant. The clear solutions, after boiling, may be 
mixed with hydrochloric acid without giving a precipitate. 

Sulphuretted hydrogen produces no change, if the cobalt be in combination 
with a strong acid. 

Sulphide of ammonium throws down black sulphide of cobalt. 



Oxide of cobalt is remarkable for the magnificent blue colour it communi- 
cates to glass : indeed this is a character by which its presence may be most 
easily detected, a very small portion of the substance to be examined being 
fused with borax on a loop of platinum wire before the blowpipe. The sub- 
stance called smalt, used as a pigment, consists of glass coloured by oxide of 
cobalt ; it is thus made : — The cobalt- ore is roasted until nearly free from 
arsenic, and then fused with a mixture of carbonate of potassa and quartz- 
sand, free from oxide of iron. Any nickel that may happen to be contained 
in the ore then subsides to the bottom of the crucible as arsenide ; this is 
the speiss of which mention has already been made. The glass, when com- 
plete, is removed and poured into cold water ; it is afterwards groiind to 
powder and elutriated. Cobalt-ultramarine is a fine blue colour prepared by 
mixing 16 parts of freshly precipitated alumina with 2 parts of phosphate or 
arsenate of cobalt: this mixture is dried and slowly heated to redness. By 
daylight the colour is pure blue, but by artificial light it is violet. Zaffer is 
the roasted cobalt ore mixed with a quantity of siliceous sand, and reduced 
to fine powder ; it is used in enamel-painting. A mixture in due proportions 
of the oxides of cobalt, manganese, and iron is used for giving a fine black 
colour to glass. 



Zinc is a somewhat abundant metal ; it is found in the state of carbonate 
und sulphide associated with lead ores in many districts, both in Britain and 



zinc. 273 

on the Continent ; large supplies are obtained from Silesia. The native car- 
bonate, or calamine, is the most valuable of the zinc ores, and is preferred 
for the extraction of the metal ; it is first roasted to expel water and carbonic 
acid, mixed with fragments of coke or charcoal, and then distilled at a full 
red-heat in a large earthen retoi't; carbonic oxide escapes, while the reduced 
metal volatilizes and is condensed by suitable means, generally with minute 
quantities of arsenic. 

Zinc is a bluish- white metal, which slowly tarnishes in the air ; it has a 
lamellar, crystalline structure, a density varying from 6-8 to 7*2, and is, 
under ordinary circumstances, brittle. Between 250° (121°C) and 300° 
(149°C) it is, on the contrary, malleable, and may be rolled or hammered 
without danger of fracture, and, what is very remarkable, after such treat- 
ment, retains it malleability when cold : the sheet-zinc of commerce is thus 
made. At 400° (204° -4C) it is so brittle that it may be reduced to powder. 
At 778° (411°-6C) it melts : at a bright red-heat it boils v aud volatilizes, and, 
if air, be admitted, burns with a splendid green light, generating the oxide. 
Dilute acids dissolve zinc very readily ; it is constantly employed in this 
manner in preparing hydrogen gas. 

The equivalent of zinc has been fixed at 32 G ; its symbol is Zn. 

Protoxide of zinc, ZnO. — Only one oxide of this metal is known to 
exist; it is a strong base, isomorphous with magnesia ; it is prepared either 
by burning zinc in atmospheric air, or by heating to redness the carbonate. . 
Oxide of zinc is a white tasteless powder, insoluble in water, but freely dis- 
solved by acids. "When heated it is yellow, but turns white again on cooling. 

Sulphate of zinc ; white vitriol ; ZnO, S0 3 -|-7HO. This salt is hardly 
to be distinguished by the eye from the sulphate of magnesia ; it is pre- 
pared by dissolving the metal in dilute sulphuric acid, or, more economically, 
by roasting the native sulphide, or blende, which by absorption of oxygen 
becomes in great part converted into sulphate of the oxide. The altered 
mineral is thrown hot into water, and the salt obtained by evaporating the 
clear solution. Sulphate of zinc has an astringent metallic taste, and is 
used in medicine as an emetic. The crystals dissolve in 1\ parts of cold, 
and in a much smaller quantity of hot water. Crystals containing 6 equiva- 
lents of water have been observed. Sulphate of zinc forms double salts 
with the sulphates of potassa and ammonia. 

Carbonate of zinc, ZnO,C0 2 . — The neutral carbonate is found native ; 
the white precipitate obtained by mixing solutions of zinc and of alkaline 
carbonates is a combination of carbonate and hydrate. When heated to 
redness, it yields pure oxide of zinc. 

Chloride of zinc, ZnCl. — The chloride may be prepared by heating 
metallic zinc in chlorine ; by distilling a mixture of zinc-filings and corrosive 
sublimate ; or, more easily, by dissolving zinc in hydrochloric acid. It is a 
nearly white, translucent, fusible substance, very soluble in water and 
alcohol, and very deliquescent. A strong solution of chloride of zinc is 
sometimes used as a bath for obtaining a graduated heat above 212° 
(100°C). Chloride of zinc unites with sal-ammoniac and chloride of potas- 
sium to double salts ; the former of these, made by dissolving an equivalent 
of zinc in the requisite quantity of hydrochloric acid, and then adding an 
equivalent of sal-ammoniac, is very useful in tinning and soft-soldering 
copper and iron. 

A salt of zinc is easily distinguished by appropriate reagents. 

Caustic potassa and soda give a white precipitate of hydrate, freely soluble 
in excess of alkali. 

Ammonia behaves in the same manner ; an excess re-dissoives the precipj 
tate instantly. 



274 CADMIUM — BISMUTH. 

The carbonates of potassa and soda give white precipitates, insoluble in 
excess. 

Carbonate of ammonia gives also a white precipitate, which is re-dissolved 
by an excess. 

Ferrocyanide of potassium gives a white precipitate. 

Sulphuretted hydrogen causes no change. 1 

Sulphide of ammonium throws down white sulphide of zinc. 



The applications of metallic zinc to the purposes of roofing, the construc- 
tion of water-channels, &c, are well known; it is sufficiently durable, but 
inferior in this respect to copper. 



This metal was discovered in 1817 by Stromeyer; it accompanies the ores 
of zinc, and, being more volatile than that substance, rises first in vapour 
when the calamine is subjected to distillation with charcoal. Cadmium 
resembles tin in colour, but is somewhat harder ; it is very malleable, has 
a density of 8-7. melts below 500° (260°C), and is nearly as volatile as mer- 
cury. It tarnishes but little in the air, but, when strongly heated, burns. 
Dilute sulphuric and hydrochloric acids act but little on this metal in the 
cold ; nitric acid is its best solvent. 

The equivalent of cadmium is 56 ; its symbol is Cd. 

Protoxide of cadmium, CdO. — The oxide may be prepared by igniting 
either the carbonate or the nitrate ; in the former case it has a pale brown 
colour, and in the latter a much darker tint and a crystalline aspect. Oxide 
of cadmium is infusible ; it dissolves in acids, producing a series of colourless 
salts. 

Sulphate of cadmium, CdO, S0 3 -f- 4110. — This is easily obtained by dis- 
solving the oxide or carbonate in dilute sulphuric acid ; it is very soluble in 
water, and forms double salts with the sulphates of potassa and of ammonia, 
which contain CdO,S0 3 -f KO,S0 8 -j-6HO, and CdO,S0 3 -| NH 4 0,S0 3 -f 6HO. 

Chloride of cadmium, CdCl. — This is a very soluble salt, crystallizing in 
small four-sided prisms. 

Sulphide of cadmium is a very characteristic compound, of a bright yellow 
colour, fusible at a high temperature. It is obtained by passing sulphuretted 
hydrogen gas through a solution of the sulphate, nitrate, or chloride. 



The salts of cadmium are thus distinguished : — 

Fixed caustic alkalis give a white precipitate of hydrated oxide, insoluble 
in excess. 

Ammonia gives a similar white precipitate, readily soluble in excess. 

The alkaline carbonates, and carbonate of ammonia, throw down white 
carbonate of cadmium, insoluble in excess of either precipitant. 

Sulphuretted hydrogen and sulphide of ammonium precipitate the yellow 
sulphide of cadmium. 

bismuth. 

Bismuth is found chiefly in the metallic state, disseminated through an 
earthy matrix, from which it is separated by simple exposure to heat. The 
metal is highly crystalline and very brittle; it has a reddish-white colour, 
and a density of 9-9. Cubic crystals of great beauty may be obtained by 

' "With neutral solutions, or zinc-salts of an organic acid, a white precipitate eiisues. 



BISMUTH. 275 

slo'ivly cooling a considerable mass of tins substance until solidification has 
commenced, and then piercing the crust, and pouring out the fluid residue. 
Bismuth melts at about 500° (260°C), and volatilizes at a high temperature : 
it is little oxidized by the air, but burns when strongly heated with a bluish 
flame. Nitric acid, somewhat diluted, dissolves it freely. 

The equivalent of bismuth is 213, its symbol is Bi. 

Teroxide of bismuth, Bi0 3 . — This is the base of all the salts. It is a 
straw-yellow powder, obtained by gently igniting the neutral or basic nitrate. 
It is fusible at a high temperature, and in that state acts towards siliceous 
matter as a powerful flux. 

Bismuthic acid, Bi0 5 . — If teroxide of bismuth be suspended in a strong 
solution of potassa, and chlorine be passed through this liquid, decomposition 
of water ensues ; hydrochloric acid being formed and the teroxide converted 
into the pentoxide. To separate any teroxide which may have escaped oxi- 
dation, the powder is treated with dilute nitric acid, when the bismuthic 
acid is left as a reddish powder, which is insoluble in water. This substance 
combines with bases, but the compounds are not very well known. When 
heated it loses oxygen, an intermediate oxide Bi0 4 being formed, which may 
be considered as bismuthate of bismuth, 2Bi0 4 =Bi0 3 ,Bi0 5 . 

Nitrate op bismuth, Bi0 3 ,N0 5 -j~9HO. — When bismuth is dissolved in 
moderately strong nitric acid to saturation, and the whole left to cool, large, 
colourless, transparent crystals of the neutral nitrate are deposited. Water 
decomposes these crystals ; and an acid solution containing a little bismuth 
is obtained, and a brilliant white crystalline powder is left, which varies to 
a certain extent in composition according to the temperature and the quan- 
tity of water employed, but which frequently consists of a basic nitrate of 
the teroxide Bi0 3 ,3N0 5 -f-2HO. A solution of nitrate of bismuth, free from 
any great excess of acid, poured into a large quantity of cold water, yields 
an insoluble basic nitrate, very similar in appearance to the above, but con- 
taining rather a larger proportion of teroxide of bismuth. This remarkable 
decomposition illustrates at once the basic property of water, and the feeble 
affinity of teroxide of bismuth for acids, the nitric acid dividing itself between 
the two bases. The decomposition of a neutral salt by water is by no means 
an uncommon occurrence in the history of the metals ; a solution of terchlo- 
ride of antimony exhibits the same phenomenon ; certain salts of mercury 
are affected in a similar manner, and other cases might perhaps be cited, less 
conspicuous, where the same change takes place to a smaller extent. 

The basic nitrate of teroxide of bismuth was once extensively employed as 
a cosmetic, but is said to injure the skin, rendering it yellow and leather-like. 
It has been used in medicine. 

The other salts of bismuth possess few points of interest. 



Bismuth is sufficiently characterized by the decomposition of the nitrate 
by water, and by the blackening the nitrate undergoes when exposed to the 
action of sulphuretted hydrogen gas. 

A mixture of 8 parts of bismuth, 5 parts of lead, and 3 of tin, is known 
tinder the name of fusible metal, and is employed in taking impressions from 
dies and for other purposes; it melts below 212° (100°C). The discrepan- 
cies so frequently observed between the properties of alloys and those of 
their constituent metals, plainly show that such substances must be looked 
upon as true chemical compounds, and not as mere mixtures ; in the present 
case the proof is complete, for the fusible metal has lately been obtained in 
crystals. 



276 URANIUM. 



This metal is found in a few minerals, sis pitchblende and uranite, of which 
the former is the most abundant. It appears from the recent interesting re- 
searches of M. Peligot, that the substance hitherto taken for metallic ura- 
nium, obtained by the action of hydrogen gas upon the black oxide, is not 
in reality the metal, but a protoxide, capable of uniting directly with acids, 
and, like the protoxide of manganese, not decomposable by hydrogen at a 
red-heat. The metal itself can be obtained only by the intervention of po 
tassium, applied in the same manner as in the preparation of magnesium. 
It is described as a black coherent powder, or a white malleable metal, ac- 
cording to the state of aggregation, not oxidized by air or water, but emi- 
nently combustible when exposed to heat. It unites also with great viojence 
with chlorine and with sulphur. M. Peligot admits three distinct oxides of 
uranium, besides two other compounds of the metal and oxygen, which he 
designates as suboxides. 

The equivalent of uranium is 60. Its symbol is U. 

Protoxide of uranium, UO. — This is the ancient metal ; it is prepared 
by several processes, one of which has been already mentioned. It is a 
brown powder, sometimes highly crystalline. When in minute division it is 
pyrophoric, taking fire in the air, and burning to black oxide. It forms with 
acids a series of green salts. A corresponding chloride exists, which forms 
dark green octahedral crystals, highly deliquescent and soluble in water. 
M. Peligot atti-ibutes a very extraordinary double function to this substance, 
namely, that of acting as a protoxide and forming salts with acids, and that 
of combining with chlorine or oxygen after the fashion of an elementary 
body. 

Protosesquioxide op uranium; black oxide; U 4 5 , or 2UO-f-U 2 3 . — 
The black oxide, formerly considered as protoxide, is produced when both 
protoxide and sesquioxide are strongly heated in the air, the former gaining, 
and the latter losing, a certain quantity of oxygen. It forms no salts, but 
is resolved by solution in acids into protoxide and sesquioxide. 

Sesquioxide of uranium, U 2 3 . — The sesquioxide is the best known and 
most important of the three ; it forms a number of extremely beautiful yel- 
low salts. When caustic alkali is added to a solution of nitrate of sesqui- 
oxide of uranium, a yellow precipitate of hydrated oxide falls, which, re- 
tains, however, a portion of the precipitant. The hydrate cannot be exposed 
to a heat sufficient to expel the water without a commencement of decompo- 
sition. A better method of obtaining the sesquioxide is to heat by means 
of an oil-bath the powdered and dried crystals of the nitrate to 480° (249°C), 
until no more nitrous fumes are disengaged. Its colour in this state is 
chamois-yellow. 

Nitrate of sesquioxide of uranium, TJ 2 3 ,N0 5 -|-6HO ; or (U 2 2 ) 0, NO, 
-j-tillO; U 2 2 being the supposed quasi-metal. — This nitrate is the starting 
point in the preparation of all the compounds of uranium ; it may be pre- 
pared from pitchblende by dissolving the pulverized mineral in nitric acid, 
evaporating to dryness, adding water and filtering; the liquid furnishes, by 
due evapoi'ation, crystals of nitrate of uranium, which are purified by a 
repetition of the process, and, lastly, dissolved in ether. This latter solu- 
tion yields the pure nitrate. 

The green salts of uranium are peroxidized by boiling with nitric acid. 



A yellow precipitate with caustic alkalis, convertible by heat into black 
oxide; a brown precipitate with sulphide of ammonium; and none at all 
with pulohuietted hydrogen gas, sufficiently characterize the salts of sesqui- 



copper. 277 

oxide of uranium. A solution suspected to contain protoxide may be boiled 
with a little nitric acid, and then examined. 



The only application of uranium is that to enamel-painting and the stain- 
ing of glass ; the protoxide giving a fine black colour, and the sesquioxide 
a delicate yellow. 

COPPER. 

Copper is a metal of great value in the arts of life ; it sometimes occur 
in the metallic state, crystallized in octahedrons, but is more abundant ii 
the condition of red oxide, and in that of sulphide combined with sulphide 
of iron, or yellow copper ore. Large quantities of the latter substance are 
annually obtained from the Cornish mines and taken to South Wales for re- 
duction, which is effected by a somewhat complex process. The principle 
of this may, however, be easily made intelligible. The v ore is roasted in a 
reverberatory furnace, by which much of the sulphide of iron is converted 
into oxide, while the sulphide of copper remains unaltered. The product 
of this operation is then strongly heated with siliceous sand; the latter 
combines with the oxide of iron to a fusible slag, and separates from the 
heavier copper-compound. When the iron has, by a repetition of these pro- 
cesses been got rid of, the sulphide of copper begins to decompose in the 
flame-furnace, losing its sulphur and absorbing oxygen ; the temperature is 
then raised sufficiently to reduce the oxide thus produced, by the aid of car- 
bonaceous matter. The last part of the operation consists in thrusting into 
the melted metal a pole of birch-wood, the object of which is probably to 
reduce a little remaining oxide by the combustible gases thus generated. 
Large quantities of extremely valuable ore, chiefly carbonate and red oxide, 
have lately been obtained from South Australia. 

Copper has a well-known yellowish-red colour, a specific gravity of 8-96, 
and is very malleable and ductile ; it is an excellent conductor of heat and 
electricity ; it melts at a bright red-heat, and seems to be a little volatile at 
a very high temperature. Copper undergoes no change in dry air; exposed 
to a moist atmosphere, it becomes covered with a strongly adherent green 
crust, consisting in a great measure of carbonate. Heated to redness in 
the air, it is quickly oxidized, becoming covered with a black scale. Dilute 
sulphuric and hydrochloric acids scarcely act upon copper; boiling oil of 
vitriol attacks it with evolution of sulphurous acid ; nitric acid, even dilute, 
dissolves it readily with evolution of binoxide of nitrogen. Two oxides are 
known which form salts ; a third, or peroxide, is said to exist. 

The equivalent of copper is 31-7; its symbol Cu. 

Protoxide of copper ; black oxide ; CuO. — This is the base of the 
ordinary blue and green salts. It is prepared by calcining metallic copper 
at a red-heat, with full exposure to air, or, more conveniently, by heating to 
redness the nitrate, which suffers complete decomposition. When a salt of 
this oxide is mixed with caustic alkali in excess, a bulky pale blue precipi- 
tate of hydrated oxide falls, which, when the whole is raised to the boiling- 
point, becomes converted into a heavy dark brown powder ; this also is an- 
hydrous oxide of copper, the hydrate suffering decomposition, even in 
contact with water. The oxide prepared at a high temperature is perfectly 
black and very dense. Protoxide of copper is soluble in acids, and forms a 
series of very important salts, being isomorphous with magnesia. 

Suboxide of copper ; red oxide ; Cu 2 0. — The suboxide may be obtained 
by heating in a covered crucible a mixture of 5 parts of black oxide and 4 
parts of fine copper-filings; or by adding grape-sugar to a solution of sul- 
phate of copper, and then putting in an excess of caustic potassa ; the blue 
solution, heated to ebullition, is reduced by the sugar and deposits suboxide 
24 



278 copper. 

It often occurs in beautifully transparent ruby-red crystals, associated with 
other ores of copper, and can be obtained in this state by artificial means. 
This substance forms colourless salts with acids, which are exceedingly 
instable, and tend to absorb oxygen. The suboxide communicates to glass a 
magnificent red tint, while that given by the protoxide is green. 

Sulphate of copper; blue vitriol; CuO,S0 3 -(-5HO. — This beautiful 
salt is prepared by dissolving oxide of copper in sulphuric acid, or, at less 
expense, by oxidizing the sulphide. It forms large blue crystals, soluble in 
4 parts of cold and 2 of boiling water ; by heat it is rendered anhydrous and 
nearly white, and a very high temperature decomposed. Sulphate of copper 
combines with the sulphates of potassa and of ammonia, forming pale blue 
salts which contain 6 equivalents of water, and also with ammonia, gene 
rating a remarkable compound of deep blue colour, capable of crystallizing. 

Nitrate of copper, CuO,N0 5 -f- 3HO. — The nitrate is easily made by 
dissolving the metal in nitric acid ; it forms deep blue crystals, very soluble 
and deliquescent. It is highly corrosive. An insoluble subnitrate is known ; 
it is green. Nitrate of copper also combines with ammonia. 

Carbonates of copper. — When carbonate of soda is added in excess to 
a solution of sulphate of copper, the precipitate is at first pale blue and 
flocculent, but by warming it becomes sandy, and assumes a green tint ; in 
this state it contains CuO,C0 2 -|-CuO,HO-|-HO. This substance is prepared 
as a pigment. The beautiful mineral malachite has a similar composition, 
but contains one equivalent of water less. Another natural compound, not 
yet artificially imitated, occurs in large transparent crystals of the most 
intense blue ; it contains 2(CuO,C0 2 )-f-CuO,HO. Verditer, made by decom- 
posing nitrate of copper by chalk, is said, however, to have a somewhat 
similar composition. 

Chloride of copper, CuCl-f-2HO. — The chloride is most easily prepared 
by dissolving the black oxide in hydrochloric acid, and concentrating the 
green solution thence resulting. It forms green crystals, very soluble in 
water and in alcohol ; it colours the flame of the latter green. "When gently 
heated, it parts with its water of crystallization and becomes yellowish- 
brown ; at a high temperature it loses half its chlorine and becomes con- 
verted into the subchloride. The latter is a white fusible substance, but 
little soluble in water, and prone to oxidation ; it is formed when copper- 
filings or copper-leaf are put into chlorine gas. 

Arsenite of copper; Scheele's green. — This is prepared by mixing 
solutions of sulphate of copper and arsenite of potassa ; it falls as a bright 
green insoluble powder. 



The characters of the protosalts of copper are well marked. 

Caustic of potassa gives a pale blue precipitate of hydrate, becoming 
blackish-brown anhydrous protoxide on boiling. 

Ammonia also throws down the hydrate ; but, when in excess, re-dissolvea 
it, yielding an intense purplish blue solution. 

Carbonates of potassa and soda give pale blue precipitates, insoluble in 
excess. 

Carbonate of ammonia, the same, but soluble with deep blue colour. 

Ferrocyanide of potassium gives a fine red-brown precipitate of ferrocya- 
nide of copper. 

Sulphuretted hydrogen and sulphide of ammonium afford black sulphida 
of copper. 



The alloys of copper are of great importance. Brass consists of copper 
alloyed with from 28 to 34 per cent, of zinc ; the latter may be added di- 



LEAD. 279 

rectly to the melted copper, or granulated copper may be heated with cala- 
mine and charcoal-powder, as in the old process. Gun-metal, a most 
trustworthy and valuable alloy, consists of 90 parts copper and 10 tin. Bell 
and speculum metal contain a still larger proportion of tin ; these are brittle, 
•especially the last-named. A good bronze for statues is made of 91 parts 
copper, 2 parts tin, 6 parts zinc, and 1 part lead. The brass of the ancients 
is an alloy of copper with tin. 



This abundant and useful metal is altogether obtained from the native sul- 
phide, or galena, no other lead-ore being found in quantity. The reduction is 
effected in a reverberatory furnace, into which the crushed lead ore is intro- 
duced and roasted for some time at a dull red-heat, by which much of the 
sulphide becomes changed by oxidation to sulphate. The contents of the 
furnace are then thoroughly mixed, and the temperature raised, when the 
sulphate and sulphide react upon each other, producing sulphurous acid and 
metallic lead. 1 

Lead is a soft bluish metal, possessing very little elasticity ; its specific 
gravity is 11-45. It may be easily rolled out into plates, or drawn into coarse 
wire, but has a very trifling degree of strength. Lead melts at 600° (315° -5C) 
or a little above, and at a white-heat boils and volatilizes. By slow cooling 
it may be obtained in octahedral crystals. In moist air this metal becomes 
coated with a film of grey matter, thought to be suboxide, and when exposed 
to the atmosphere in a melted state it rapidly absorbs oxygen. Dilute acids, 
with the exception of nitric, act but slowly upon lead. Chemists are fami- 
liar with four oxides of lead, only one of which possesses basic properties. 

The equivalent of lead is 103-7 ; its symbol is Pb. 

Protoxide ; litharge : massicot ; PbO. — This is the product of the 
direct oxidation of the metal. It is most conveniently prepared by heating 
the carbonate to dull redness ; common litharge is impure protoxide which 
has undergone fusion. Protoxide of lead has a delicate straw-yellow colour, 
is very heavy, and slightly soluble in water, giving an alkaline liquid. At a 
red-heat it melts, and tends to crystallize on cooling. In a melted state it 
attacks and dissolves siliceous matter with astonishing facility, often pene- 
trating an earthen crucible in a few minutes. It is easily reduced when 
heated with organic substances of any kind containing carbon or hydrogen. 
Protoxide of lead forms a large class of salts, which are colourless if the acid 
itself be not coloured. 

Red oxide ; red-lead ; Pb 3 4 , or 2PbO-}-Pb0 2 . — The composition of 
this substance is not very constant ; it is prepared by exposing for a long 
time to the air, at a very faint red-heat, protoxide of lead which has not been 
fused ; it is a brilliant red and extremely heavy powder, decomposed with 
evolution of oxygen by a strong heat, and converted into a mixture of pro- 
toxide and binoxide by acids. It is used as a cheap substitute for vermilion. 

Binoxide of lead ; puce or brown oxide ; Pb0 2 . — This compound is 
obtained without difficulty by digesting red-lead in dilute nitric acid, when 
nitrate of protoxide is dissolved out and insoluble binoxide left behind in the 
form of a deep brown powder. The binoxide is decomposed by a red-heat, 
yielding up one-half of its oxygen. Hydi*ochloric acid converts it into chlo- 
ride of lead with disengagement of chlorine ; hot oil of vitriol forms with it 

f Oxide of f Lead Free. 

1 Sulphate of! lead | Oxygen -———-—— -^^ 2 Sulphurous acid. 

lead j Sulphuric j Sulphur Z^^^^ 

[_ acid 1 3 Oxygen 
J Sulphur" 



Sulphide of lead j "^ ^ 



280 LEAD. 

sulphate of lead, and liberates oxygen. The binoxide is very useful in sepa- 
rating sulphurous acid from certain gaseous mixtures, sulphate of lead being 
then produced. 

Suboxide of lead, Pb 2 0. — When oxalate of lead is heated to dull redness 
in a retort, a grey pulverulent substance is left, which is resolved by acids 
into protoxide of lead and metal. It absorbs oxygen with great rapidity 
when heated, and even when simply moistened with water and exposed to 
the air. 

Nitrate of lead, PbO,N0 5 . — The nitrate may be obtained by dissolving 
carbonate of lead in nitric acid, or by acting directly upon the metal by the 
same agent with the aid of heat ; it is, as already noticed, a by-product in 
the preparation of the binoxide. It crystallizes in anhydrous octahedrons, 
which are usually milk-white and opaque ; it dissolves in 1\ parts of cold 
water, and is decomposed by heat, yielding nitrous acid, oxygen, and pro- 
toxide of lead, which obstinately retains traces of nitrogen. When a solution 
of this salt is boiled with an additional quantity of oxide of lead, a portion 
of the latter is dissolved, and a basic nitrate generated, which may be had 
in crystals. Carbonic acid separates this excess of oxide in the form of a 
white compound of carbonate and hydrate of lead. 

Neutral and basic compounds of oxide of lead with nitrous, and the elements 
of hyponitric acid, have been described. These last are probably formed by 
the combination of a nitrite with a nitrate. 

Carbonate of lead; white-lead; PbO,C0 2 .— Carbonate of lead is some- 
times found beautifully crystallized in long white needles, accompanying 
other metallic ores. It may be prepared by precipitating in the cold a solu- 
tion of the nitrate or acetate by an alkaline carbonate ; when the lead solu- 
tion is boiling, the precipitate is a basic salt, containing 2(PbO,C0 2 )-f-HO, 
PbO ; it is also manufactured to an immense extent by other means for the use 
of the painter. Pure carbonate of lead is a soft, white powder, of great 
specific gravity, insoluble in water, but easily dissolved by dilute nitric or 
acetic acid. 

Of the many methods put in practice, or proposed, for making white-lead, 
the two following are the most important and interesting : — One of these 
consists in forming a basic nitrate or acetate of lead by boiling finely pow- 
dered litharge with the neutral salt. This solution is then brought into con- 
tact with carbonic acid gas ; all the excess of oxide previously taken up by 
the neutral salt is at once precipitated as white-lead. The solution strained 
or pressed from the latter is again boiled with litharge, and treated with car- 
bonic acid, these processes being susceptible of indefinite repetition, when 
the little loss of neutral salt left in the precipitates is compensated. The 
second, and by far the more ancient method, is rather more complex, and at 
first sight not very intelligible. A great number of earthen jars are pre- 
pared, into each of which is poured a few ounces of crude vinegar ; a roll 
of sheet-lead is then introduced in such a manner that it shall neither touch 
the vinegar nor project above the top of the jar. The vessels are next ar- 
ranged in a large building, side by side, upon a layer of stable manure, or, 
still better, spent-tan, and closely covered with boards. A second layer of 
tan is spread upon the top of the latter, and then a second series of pots ; 
these are in turn covered with boards and decomposing bark, and in this 
manner a pile of many alternations is constructed. After the lapse of a con- 
siderable time the pile is taken down and the sheets of lead removed and 
carefully unrolled ; they are then found to be in great part converted into 
carbonate, which merely requires washing and grinding to be fit for use. 
The nature of this curious process is generally explained by supposing the 
vapour of vinegar raised by the high temperature of the fermenting matter 
merely to act as a carrier between the carbonic acid evolved from the tan. 



LEAD 281 

and the oxide of lead formed under the influence of the acid vapour ; a neu- 
tral acetate, a basic acetate, and a carbonate being produced in succession, 
the action gradually travelling from the surface inwards. The quantity of 
acetic acid used is, in relation to the lead, quite trifling, and cannot directly 
contribute to the production of the carbonate. A preference is still given 
to the product of this old mode of manufacture on account of its superiority 
of opacity, or body, over that obtained by precipitation. Commercial "white- 
lead, however prepared, always contains a certain proportion of hydrate. 

When clean metallic lead is put into pure water and exposed to the atmo- 
sphere, a white, crystalline, scaly powder begins to show itself in a few 
hours, and very rapidly increases in quantity. This substance may consist 
of hydrated protoxide of lead, formed by the action of the oxj^gen dissolved 
in the water and from the lead. It is slightly soluble, and may be readily 
detected in the water. In most cases, however, the formation of this deposit 
is due to the action of the carbonic acid dissolved in the water; it consists 
of carbonate in combination with hydrate, and is very insoluble in water. 
When common river or spring water is substituted for the pure liquid, this 
effect is less observable, the little sulphate, almost invariably present, causing 
the deposition of a very thin but closely adherent film of sulphate of lead 
upon the surface of the metal, which protects it from farther action. It is 
on this account that leaden cisterns are used with impunity, at least in most 
cases, for holding water ; if the latter were quite pure, it would be speedily 
contaminated with lead, and the cistern be soon destroyed. Natural water 
highly charged with carbonic acid cannot, under any circumstances, be kept 
in lead, or passed through leaden pipes with safety, the carboriate, though 
very insoluble in pure water, being slightly soluble in water containing car- 
bonic acid. 

Chloride of lead, PbCl. — This salt is prepared by mixing strong solu- 
tions of acetate of lead and chloride of sodium ; or by dissolving litharge in 
boiling dilute hydrochloric acid, and setting aside the filtered solution to 
cool. Chloride of lead crystallizes in brilliant, colourless needles, which 
require 135 parts of cold water for solution. It is anhydrous ; it melts when 
heated, and solidifies on cooling to a horn-like substance. 

Iodide of lead, Pbl. — The iodide of lead separates as a brilliant yellow 
precipitate when a soluble salt of lead is mixed with iodide of potassium. 
This compound dissolves in boiling water, yielding a colourless solution, which 
deposits the iodide on cooling in splendid golden-yellow scales. 



The soluble salts of lead thus behave with reagents : — 

Caustic potassa and soda precipitate a white hydrate, freely soluble in 
excess. 

Ammonia gives a similar white precipitate, not soluble in excess.' 

The carbonates of potassa, soda, and ammonia, precipitate carbonate of 
lead, insoluble in excess. 

Sulphuric acid or a sulphate causes a white precipitate of sulphate of lead, 
insoluble in nitric acid. 

Sulphuretted hydrogen and sulphide of ammonium throw down black 
sulphide of lead. 



An alloy of 2 parts of lead and 1 of tin constitutes plumber's solder: these 
proportions reversed give a more fusible compound called fine solder. The 
lead employed in the manufacture of shot is combined with a little arsenic. 

1 Ammonia gives no immediate precipitate with the acetate. 

24 * 



282 tin 



SECTION V. 

OXIDABLE METALS PROPER, WHOSE OXIDES FORM WEAK 
BASES OR ACIDS. 



This valuable metal occurs in the state of oxide, and more rarely as sul- 
phide ; the principal tin mines are those of the Erzgebirge in Saxony and 
Bohemia, Malacca, and more especially Cornwall. In Cornwall the tin-stone 
is found as a constituent of metal bearing veins, associated with copper ore, 
in granite and slate-rocks ; and as an alluvial deposit, mixed with rounded 
pebbles, in the beds of several small rivers. The first variety is called mine- 
and the second stream-tin. Oxide of tin is also found disseminated through 
the rock itself in small crystals. 

To prepare the ore for reduction, it is stamped to powder, washed, to 
separate as much as possible of the earthy matter, and roasted to expel 
sulphur and arsenic ; it is then strongly heated with coal, and the metal thus 
obtained cast into large blocks, which, after being assayed, receive the stamp 
of the Duchy. Two varieties of commercial tin are known, called grain- and 
bar-tin ; the first is the best ; it is prepared from the stream ore. 

Pure tin has a white colour, approaching to that of silver ; it is soft and 
malleable, and when bent or twisted emits a peculiar crackling sound ; it ha3 
a density of 7-3 and melts at 442° (227°-77C). Tin is but little acted upon 
by air and water, even conjointly ; when heated above its melting-point it 
oxidizes rapidly, becoming converted into a whitish powder, used in the arts 
for polishing, under the name of putty-powder. The metal is easily attacked 
and dissolved by hydrochloric acid, with evolution of hydrogen ; nitric acid 
acts with great energy, converting it into a white h3 r drate of the binoxide. 
There are two well-marked oxides of tin, which act as feeble bases or acids, 
according to circumstances, and a third, which has been less studied. 

The equivalent of tin is 58 ; its symbol is Sn. 

Protoxide of tin, SnO. — When solution of protochloride of tin is mixed 
with carbonate of potassa, a white hydrate of the protoxide fall?, the car- 
bonic acid being at the same time extricated. When this is carefully washed, 
dried, and heated in an atmosphere of carbonic acid, it loses water, and 
changes to a dense black powder, which is permanent in the air, but takes 
fire on the approach of a red-hot body, and burns like tinder, producing 
binoxide. The hydrate is freely soluble in caustic potassa; the solution 
decomposes by keeping into metallic tin and binoxide. 

Sesquioxide of tin, Sn 2 3 . — The sesquioxide is produced by the action 
of hydra ted sesquioxide of iron upon protochloride of tin ; it is a greyish, 
Blimy substance, soluble in hydrochloric acid, and in ammonia. This oxide 
has been but little examined. 

Binoxide of tin, Sn0 2 . — This substance is obtained in two different states, 
having properties altogether dissimilar. When bichloride of tin is precipi- 
tated by an alkali, a white bulky hydrate appears, which is freely soluble'in 



tin. 282 

acids. If, on the other hand, the bichloride be boiled with excess of nitric 
acid, or if that acid be made to act directly on metallic tin, a white sub- 
stance is produced, which refuses altogether to dissolve in acids, and pos- 
sesses properties differing in other respects from those of the first modifica- 
tion. Both these varieties of binoxide of tin have the same composition, 
and when ignited, leave the pure binoxide of a pale lemon-yellow tint. 
Both dissolve in caustic alkali, and are precipitated with unchanged proper- 
ties by an acid. The two hydrates redden litmus-paper. 1 

Protochloride of tin, SnCl. — The protochloride is easily made by dis- 
solving metallic tin in hot hydrochloric acid. It crystallizes in needles con- 
taining 2 equivalents of water, which are freely soluble in a small quantity 
of water, but are apt to be decomposed in part when put into a large mass, 
unless hydrochloric acid in excess be present. The anhydrous chloride may 
be obtained by distilling a mixture of calomel and powdered tin, prepared 
by agitating the melted metal in a wooden box until it solidifies. The chlo- 
ride is a grey, resinous-looking substance, fusible below redness, and volatile 
at a high temperature. Solution of protochloride of tin is employed as a 
deoxidizing agent ; it reduces the salts of mercury and other metals of the 
same class. 

Bichloride or perchloride of tin, SnCl 2 . — This is an old and very cu- 
rious compound, formerly called fuming liquor of Libavius. It is made by 
exposing metallic tin to the action of chlorine, or, more conveniently, by 
distilling a mixture of 1 part of powdered tin, and 5 parts of corrosive sub- 
limate. The bichloride is a thin, colourless, mobile liquid; it boils at 248° 
(120°C), and yields a colourless invisible vapour. It fumes in the air, and 
when mixed with a third part of water, solidifies to a crystalline mass. The 
solution of bichloride is much employed by the dyer as a mordant ; it is com- 
monly prepared by dissolving metallic tin in a mixture of hydrochloric and 
nitric acids, care being taken to avoid too great elevation of temperature. 

Sulphides op tin. — Proto sulphide, SnS, is prepared by fusing tin with ex- 
cess of sulphur, and strongly heating the product. It is a lead-grey, brittle 
substance, fusible by a red-heat, and soluble with evolution of sulphuretted 
hydrogen in hot hydrochloric acid. A sesquisulphide may be formed by gently 
heating the above compound with a third of its weight of sulphur ; it is yel- 
lowish-grey, and easily decomposed by heat. Bisulphide, SnS 2 , or Mosaic 
gold, is prepared by exposing to a low red-heat, in a glass flask, a mixture 
of 12 parts of tin, 6 of mercury, 6 of sal-ammoniac, and 7 of flowers of 
sulphur. Sal-ammoniac, cinnabar, and protochloride of tin sublime, while 
the bisulphide remains at the bottom of the vessel in the form of brilliant 
gold-coloured scales ; it is used as a substitute for gold-powder. 

Salts of tin are thus distinguished : — 

Protoxide. 
Caustic alkalis ; white hydrate, soluble in excess. 
Ammonia ; carbonates of potassa, ^ ,„, -,17. ■, • n -. t 

soda, and ammonia P hlte h ^ drate ' nearl ? soluble m 

excess. 

Suip^ precipitate of protosulphide. 

Binoxide. 
Caustic alkalis ; white hydrate, soluble in excess. 
Ammonia ; white hydrate, slightly soluble in excess. 

1 Fremy has called the first of these oxides stannic acid S11O2. The second he has named 
metastannic acid Sn 5 0io. See als-o H. Rose Pogg. Ann. lxxv. 1, who thinks that there are 
other modifications of this oxide of tin. 



234 TUNGSTEN — MOLYBDENUM. 

Alkaline carbonates ; white hydrates, slightly soluble in excess 
Carbonate of ammonia; -white hydrate, insoluble. 
Sulphuretted hydrogen ; yellow precipitate of sulphide. 
Sulphide of ammonium ; the same, soluble in excess. 

Terchloride of gold, added to a dilute solution of protochloride of tin, 
gives rise to a brownish-purple precipitate, called purple of Cassius, very 
characteristic, whose nature is not thoroughly understood ; it is supposed to 
be a combination of oxide of gold and sesquioxide of tin, in which the latter 
acts as an acid. Heat resolves it into a mixture of metallic gold and binox- 
ide of tin. Purple of Cassius is employed in enamel-painting. 



The useful applications of tin are very numerous. Tinned-plate consists 
of iron superficially alloyed with this metal ; pewter, of the best kind, is 
chiefly tin, hardened by the admixture of a little antimony, &c. Cooking 
vessels of copper are usually tinned in the interior. 

TUNGSTEN (WOLFRAMITTM). 

Tungsten is found, as tungstate of protoxide of iron, in the mineral wolf- 
ram, tolerable abundant in Cornwall ; a native tungstate of lime is also oc- 
casionally met with. Metallic tungsten is obtained in the state of a dark 
grey powder, by strongly heating tungstic acid in a stream of hydrogen, but 
requires for fusion an exceedingly high temperature. It is a white metal, 
very hard and brittle; it has a density of 17-4. Heated to redness in the 
air, it takes fire, and reproduces tungstic acid. 

The equivalent of tungsten is 92, its symbol is W (wolframium). 

Binoxide of tungsten, W0 2 . — This is most easily prepared by exposing 
tungstic acid to hydrogen, at a temperature which does not exceed dull red- 
ness. It is a brown powder, sometimes assuming a crystalline appearance 
and an imperfect metallic lustre. It takes fire when heated in the air, and 
burns, like the metal itself, to tungstic acid. The binoxide forms no salts 
with acids. 

■ Tungstic acid, W0 3 . — When tungstate of lime can be obtained, simple 
digestion in hot nitric acid is sufficient to remove the base, and liberate the 
tungstic acid in a state of tolerable purity; its extraction from wolfram, 
which contains tungstic acid or oxide of tungsten in association with the 
oxides of iron and manganese, is more difficult. Tungstic acid is a yellow 
powder, insoluble in water, and freely dissolved by caustic alkalis. When 
strongly ignited in the open air, it assumes a greenish tint. 

Intermediate or blue oxide op tungsten, W 2 5 ,=W0 2 ,W0 3 . — This sub- 
stance is obtained by heating tungstate of ammonia, or by exposing the 
brown binoxide to the action of hydrogen at a very low temperature. The 
same compound appears to be produced if tungstic acid be separated from 
one of its salts, by hydrochloric acid and the liquid be digested with metallic 
zinc, when the solution or the precipitate assumes a beautiful blue colour, 
which is verj' characteristic of this metal. 

Two chlorides and two sulphides of tungsten are known to exist. 

molybdenum. 

Metallic molybdenum is obtained by exposing molybdic acid in a charcoal- 
lined crucible to the most intense heat that can be obtained. It is a white, 
brittle, and exceedingly infusible metal, having a density of 8-6, and oxi- 
jizing, when heated in the air, to molybdic acid. 

The equivalent of molybdenum is 46; its symbol is Mo. 

Pbotoxidk oi molybdenum, MoO. — Molybdate of potassa is mixed with 



VANADIUM. 285 

excess of hydro chloric acid, by which the molybdic acid first precipitated is 
re-dissolved ; into this acid solution zinc is put : a mixture of chloride of 
zinc and protochloride of molybdenum results. A large quantity of caustic 
potassa is then added, which precipitates a black hydrate of the protoxide 
of molybdenum, and retains in solution the oxide of zinc. The freshly pre- 
cipitated protoxide is soluble in acids and in carbonate of ammonia ; when 
heated in the air, it burns to binoxide. 

Binoxide of molybdenum, Mo0 2 . — This is obtained in the anhydrous con- 
dition by heating molybdate of soda with sal-ammoniac, the molybdic acid 
being reduced to binoxide by the hydrogen of the ammoniacal salt ; or, in a 
hydrated condition, by digesting metallic copper in a solution of molybdic 
acid in hydrochloric acid, until the liquid assumes a red colour, and then 
adding a large excess of ammonia. The anhydrous binoxide is deep brown, 
and insoluble in acids ; the hydrate resembles hydrate of sesquioxide of iron, 
and dissolves in acids, yielding red solutions. It is concerted into molybdic 
acid by strong nitric acid. 

Molybdic acid, Mo0 3 . — The native bisulphide of molybdenum is roasted, 
at a red-heat, in an open vessel, and the impure molybdic acid thence re- 
sulting dissolved in ammonia. The filtered solution is evaporated to dryness, 
the salt taken up by water, and purified by crystallization. It is, lastly, 
decomposed by heat, and the ammonia expelled. Molybdic acid is a white 
crystalline powder, fusible at a red-heat, and slightly soluble in water. It 
is dissolved with ease by the alkalis. It forms two series of salts, namely, 
neutral molybdates MO,Mo0 3 , and ac^d molybdates MO,2Mo0 3 . Three 
chlorides, and as many sulphides of molybdenum, are described. 

VANADIUM. 

Vanadium is found, in small quantity; in one of the Swedish iron ores, 
and also as vanadate of lead. It has also been discovered in the iron slag of 
Staffordshire. The most successful process for obtaining the metal is said 
to be the following : — The liquid chloride of vanadium is introduced into a 
bulb, blown in a glass tube, and dry ammoniacal gas passed over it ; the 
latter is absorbed, and a white saline mass produced. When this is heated 
by the flame of a spirit-lamp, chloride of ammonium is volatilized, and 
metallic vanadium left behind. It is a white brittle substance, of perfect 
metallic lustre, and a very high degree of infusibility ; it is neither oxidized 
by air or water, nor attacked by sulphuric, hydrochloric, or even hydrofluoric 
acid ; aqua regia dissolves it, yielding a deep bluo solution. 

The equivalent of vanadium is 68-6 ; its symbol is V. 

Protoxide of vanadium, VO. — This is prepared by heating vanadic acid 
in contact with charcoal or hydrogen ; it has a black colour, and imperfect 
metallic lustre, conducts electricity, and is very infusible. Heated in the 
air, it burns to binoxide. Nitric acid produces the same effect, a blue nitrate 
of the binoxide being generated. It does not form salts. 

Binoxide of vanadium, V0 2 . — The binoxide is obtained by heating a 
mixture of 10 parts protoxide of vanadium, and 12 of vanadic acid in a vessel 
filled with carbonic acid gas ; or by adding a slight excess of carbonate of 
soda to a salt of the binoxide; in the latter case it falls as a greyish-white 
hydrate, readily becoming brown by absorption of oxygen. The anhydrous 
oxide is a black insoluble powder, convertible by heat and air into vanadic 
acid. It forms a series of blue salts, which have a tendency to become green 
and ultimately red, by the production of vanadic acid. Binoxide of vanadium 
also unites with alkalis. 

Vanadic acid, V0 3 . — The native vandate of lead is dissolved in nitric 
acid, and the lead and arsenic precipitated by sulphuretted hydrogen, which 
at the same time reduces the vanadic acid to binoxide of vanadium. The 



2.J$ TANTALUM — NIOBIUM AND PELOPIUM. 

blue filtered solution is then evaporated to dryness, and the residue digested 
in ammonia, which dissolves out the vanadic acid reproduced during evapo- 
ration. Into this solution a lump of sal-ammoniac is put; as that salt dis- 
solves, vanadate of ammonia subsides as a white powder, being scarcely solu- 
ble in a saturated solution of chloride of ammonium. By exposure to a tem- 
perature below redness in an open crucible, the ammonia is expelled, and 
vanadic acid left. It has a dark-red colour, and melts even below a red- 
heat ; water dissolves it sparingly, and acids with greater ease ; the solutions 
easily sutfer deoxidation. It unites with bases, forming a series of red or 
yellow salts, of which those of the alkalis are soluble in water. 

Chlorides of vanadium. — The bichloride is prepared by digesting vanadic 
acid in hydrochloric acid, passing a stream of sulphuretted hydrogen, and 
evaporating the whole to dryness. A brown residue is left, which yields a 
blue solution with water and an insoluble oxichloride. The ter -chloride is a 
yellow liquid obtained by passing chlorine over a mixture of protoxide of 
vanadium and charcoal. It is converted by water into hydrochloric and 
vanadic acids. 

Two sulphides, corresponding to the chlorides, exist. 

TANTALUM (COLUMBIUM). 

This is an exceedingly rare substance ; it is found in the minerals ianialite 
and yttro-lanlalile, and may be obtained pure by heating with potassium the 
double fluoride of tantalum and potassium. It is a grey metal, but little 
acted on by the ordinary acids, and burning to tantalic acid when heated in 
the air, or when fused with hydrate of potassa. 

The equivalent of tantalum is 184 ; its symbol is T. 

Binoxide of tantalum, T0 2 . — When tantalic acid is heated to whiteness 
in a crucible lined with charcoal, the greater part is converted into this sub- 
stance. It is a dark-brown powder, insoluble in acids, and easily changed 
by oxidation to tantalic acid. 

Tantalic acid, T0 3 . — The powdered ore is fused with three or four times 
its weight of carbonate of potassa. and the product digested with water ; 
from this solution acids precipitate a white hydrate of the body in question. 
It is soluble in acids, but forms with them no definite compounds ; with al- 
kalis it yields, on the contrary, crystallizable salts. The specific gravity of 
the acid varies 7-03 to 8-26. 

NIOBIUM AND PELOPIUM. 

The oxides of these two metals exist in the ianialite of Bodenmais in Ba- 
varia. When the supposed tantalic acid from this source is mixed with dry 
powdered charcoal, and heated to redness in a current of chlorine gas, a 
sublimate is obtained of a yellow, readily fusible, and very volatile substance, 
the chloride of pelopium, and a white, infusible, less volatile bodj 7 , the chlo- 
ride of niobium. The true chloride of tantalum, from the Finland tantalite, 
much resembles chloride of pelopium. The American tantalite contains nio- 
bic, pelopic, and tungstic acids, the former in greatest quantity. 

All these chlorides are decomposed by water, with production of hv-dro- 
chloric acid and the insoluble acids of the metals in the hydrated state. In 
properties these bodies greatly resemble each other. When heated to redness, 
they exhibit strongly the phenomenon of incandescence. While hot, tantalic 
acid remains white, pelopic acid is rendered slightly yellowish and has a spe- 
cific giavity varying from 5-79 to 637, and niobic acid becomes dark yellow, 
with a specific gravity between 4-5G and 5*26. 

Tantalum, niobium, and pelopium may be obtained in a finely-divided me- 
tallic state by the action of ammonia on their respective chlorides at a high 



TITANIUM — ANTIMONY. 28V 

temperature. So prepared, they are black, pulverulent, not acted on bj 
water, but burning, when heated in the air, to acids. 

TITANIUM. 

Crystallized oxide of titanium is found in nature in the forms of titanitt 
and analat>e. Occasionally in the slag adherent to the bottom of blast-furnaces 
in which iron ore is reduced small brilliant copper-coloured cubes, hard 
enough to scratch glass, and in the highest degree infusible are found. This 
substance, of which a single smelting furnace in the Hartz produced as much 
as 80 pounds, was formerly believed to be metallic titanium. Recent re- 
searches of Wohler, however, have shown it to be a combination of cyanide 
of titanium with nitride of titanium. AVhen these crystals are powdered, 
mixed with hydrate of potassa and fused, ammonia is evolved, and titanate 
of potassa is formed. Metallic titanium in a finely divided state may be ob- 
tained by heating fluoride of titanium and potassium with potassium. There 
are two compounds of this substance with oxygen ; viz. an oxide and an 
acid : very little is known respecting the former. 

The equivalent of titanium is 25 ; its symbol is Ti. 

Titanic acid, TiC^. — Titanate, or titauiferous iron ore, is reduced to fine 
powder and fused with twice its weight of carbonate of potassa, powdered, 
dissolved in dilute hydrofluoric acid when titanofluoride of titanium and 
potassium soon begins to separate. From its hot aqueous solution snow-like 
titanate of ammonia is precipitated by ammonia, which is easily soluble in 
hydrochloric acid, and when ignited gives pure titanic acid. When pure the 
acid is quite white ; it is, when recently precipitated from solutions, soluble 
in acids, but the solutions are decomposed by mere boiling. After ignition 
it is no longer soluble, passing over into metatitanic acid. Titanic acid, on 
the whole, very much resembles silica, and is probably often overlooked and 
confounded with that substance in analytical researches. 

Bicfiloride of titanium. — This is a colourless, volatile liquid, resembling 
bichloride of tin ; it is obtained by passing chlorine over a mixture of titanic 
acid and charcoal at a high -temperature. It unites very violently with 
water. On passing the vapour with hydrogen through a red-hot tube, 
hydrochloric acid and a new compound Ti 2 Cl 3 are formed. 

antimony. 

This important metal is found chiefly in the state of sulphide. The ore is 
freed by fusion from earthy impurities, and is afterwards decomposed by 
heating with metallic iron or carbonate of potassa, which retains the sulphur. 
Antimony has a bluish-white colour and strong lustre ; it is extremely 
brittle, being reduced to powder with the utmost ease. Its specific gravity 
is 6-8; it melts at a temperature just short of redness, and boils and vola- 
tilizes at a white-heat. This metal has always a distinct crystalline, platy 
structure, but by particular management it may be obtained in crystals, 
which are rhombohedral. Antimony is not oxidized by the air at common 
temperatures ; strongly heated, it burns with a white flame, producing ter- 
oxide, which is often deposited in beautiful crystals. It is dissolved by hot 
hydrochloric acid with evolution of hydrogen and production of terchloride. 
Nitric acid oxidizes it to antimonic acid, which is insoluble in that men- 
struum. There are three compounds of antimony and oxygen ; the first has 
doubtful basic properties, the second is indifferent, and the third is an acid. 

The equivalent of antimony is 129. Its symbol is Sb (stibium). 

Teroxide of antimony, Sb0 3 . — This compound may be prepat-ed by 
several methods : as by burning metallic antimony at the bottom of a large 
red-hot crucible, in which case it is obtained in brilliant crystals ; or by 
pouring solvtion of terchloride of antimony into water, and digesting tht 



288 ANTIMONY. 

resulting precipitate with a solution of carbonate of soda. The teroxide 
thus produced is anhydrous ; it is a pale buff-coloured powder, fusible at a 
red-heat, and volatile in a close vessel, but in contact with air, it, at a high 
temperature, absorbs oxygen and becomes changed to the intermediate oxide. 
There exists a sulphate, nitrate, and oxalate of teroxide of antimony. When 
boiled with cream of tartar (bitartrate of potassa), it is dissolved, and the 
solution yields, on evaporation, crystals of tartar-emetic, which is almost the 
only compound of teroxide of antimony with an acid which bears admixture 
with water without decomposition. An impure oxide for this purpose is 
sometimes prepared by carefully roasting the powdered sulphide in a rever- 
beratory furnace, and raising the heat at the end of the process, so as to fuse 
the product; it has long been known under the name of glass of antimony. 

Intermediate oxide, Sb0 4 = Sb0 3 ,Sb0 5 . — This is the ultimate product 
of the oxidation of the metal by heat and air ; it is a greyish white powder, 
infusible, and destitute of volatility ; it is insoluble in water and in acids, 
except when recently precipitated. When treated with tartaric acid or 
bitartrate of potassa, teroxide of antimony is dissolved, antimonic acid 
remaining behind ; alkalis, on the other hand, remove antimonic acid, ter- 
cxide of antimony being left. 

Antimonic acid, Sb0 5 . — When strong nitric acid is made to act upon 
metallic antimony, the metal is oxidized to its highest point, and antimonic 
acid produced, which is insoluble. By exposure to a heat short of redness, 
it is rendered anhydrous, and then presents the appearance of a pale straw- 
coloured powder, insoluble in water and acids. It is decomposed by a red- 
heat, yielding the intermediate oxide, with the loss of oxygen. 

Antimonic acid is likewise obtained by decomposing pentachloride of anti- 
mony and an excess of water, when, together with the metallic acid, hydro- 
acid is produced. The hydrated antimonic acid produced by the two pro- 
cesses mentioned, differs in many of its properties, and especially in its 
deportment with bases. The substance produced by nitric acid is monobasic, 
producing salts of the formula MO,Sb0 5 , the other is bibasic, and forms two 
series of salts of the composition 2MO,Sb0 5 and MO,HO,Sb0 5 . In order to 
distinguish the two modifications, M. Fremy, who first pointed out the bibasic 
nature of the acid obtained from the pentachloride, has proposed to distin- 
guish it as metantimonic acid. Among the salts of the latter, an acid 
metantimonate of potassa KO,HO,Sb0 5 -4-^HO, is to be noticed, which yields 
a precipitate with soda-salts. It is the only reagent which precipitates soda, 
but must be employed with great care and circumspection. It is obtained 
by fusing antimonic acid with an excess of potassa in a silver crucible, dis- 
solving the fused mass in a small quantity of cold water, and allowing it to 
crystallize in vacuo. The crystals which form are metantimonate of potassa 
2KO, Sb0 5 , which, when dissolved in pure water, are decomposed into free 
potassa and acid metantimonate. 

Terchloride of antimony ; butter of antimony ; SbC! 3 . — This substance 
is produced when sulphuretted hydrogen is prepared by the action of strong 
hydrochloric acid on tersulphide of antimony. The impure and highly acid 
solution thus obtained is put into a retort and distilled until each drop of 
the condensed product, on falling into the aqueous liquid of the receiver, 
produces a copious white precipitate. The receiver is then changed, and the 
distillation continued. Pure terchloride of antimony passes over, and soli- 
difies on cooling to a white and highly crystalline mass, from which the air 
requires to be carefully excluded. The same compound is formed by distil- 
ling metallic antimony in powder with 2} times its weight of corrosive subli- 
mate. Terchloride of antimony is very deliquescent ; it dissolves in strong 
hydrochloric acid without decomposition, and the solution poured into water 
gives rise to a white bulky precipitate, which, after a short time, becomes 



ANTIMONY. 289 

highly crystalliue, and assumes a pale fawn colour. This is the old powder 
of Algaroth ; it is a compound of terchloride and teroxide of antimony. Al- 
kaline solutions extract the chloride and leave teroxide of antimony. Finely 
powdered antimony thrown into chlorine gas inflames. 

Pentachoride of Antimony, corresponding to antimonic acid, is formed 
by passing a stream of chlorine gas ever gently heated metallic antimony ; a 
mixture of the two chlorides results, which may be separated by distillation.* 
The pentachloride is a colourless volatile liquid, which forms a crystalline 
compound with a small portion of water, but is decomposed by a larger quan- 
tity into antimonic and hydrochloric acids. 

Tersulphide op antimony; crude antimony; SbS 3 . — The native sulphide 
is a lead-grey, brittle substance, having a radiated crystalline texture, and 
is easily fusible. It may be prepared artificially by melting together anti- 
mony and sulphur. When a solution of tartar-emetic is precipitated by sul- 
phuretted hydrogen, a brick-red precipitate falls, which is, the same substance 
combined with a little water. If the precipitate be dried and gently heated, 
the water may be expelled without other change of colour than a little dark- 
ening, but at a higher temperature it assumes the colour and aspect of the 
native sulphide. This remarkable change probably indicates a passage from 
the amorphous to the crystalline condition. 

When powdered tersulphide of antimony is boiled in a solution of caustic 
potassa, it is dissolved, teroxide of antimony and sulphide of potassium being 
produced. The latter unites with an additional quantity of tersulphide of 
antimony to a soluble sulphur-salt, in which the sulphide of potassium is the 
sulphur-base, and the tersulphide of antimony is the sulphur-acid. 

{3 eq. potassium "^---" " / 3 eq ' sul P nide o f 
^^— -""^^ \ potassium. 
3 eq. oxygen ~~^-^Z^T 
Tersulphide of j 3 eq. sulphur ~~~ - — -^-___^ . , 

antimony \ 1 eq. antimony ===-1 eq. teroxide of 

' antimony. 

The teroxide of antimony separates in small crystals from the boiling solu- 
tion when the latter is concentrated, and the sulphur-salt dissolves an extra 
proportion of tersulphide of antimony, which it again deposits on cooling as 
a red amorphous powder, containing a small admixture of teroxide of anti- 
mony and sulphide of potassium. This is the kermes mineral of the old 
chemists. The filtered solution mixed with an acid gives a salt of potassa, 
sulphuretted hydrogen, and precipitated tersulphide of antimony. Kermes 
may also be made by fusing a mixture of 5 parts tersulphide of antimony 
and 3 of dry carbonate of soda, boiling the mass in 80 parts of water, and 
filtering while hot ; the compound separates on cooling. 

Pentasulphide of antimony, SbS 5 , formerly called sulphur auratum, also 
exists ; it is a sulphur-acid. 18 parts finely powdered tersulphide of anti- 
mony, 17 parts dry carbonate of soda, 13 parts lime in the state of hydrate, 
and 3| parts sulphur, are boiled for some hours in a quantity of water; car- 
bonate of lime, antimonate of soda, pentasulphide of antimony, and sulphide 
of sodium are produced. The first is insoluble, and the second partially so ; 
the two last-named bodies, on the contrary, unite to a soluble sulphui-salt, 
which may by evaporation be obtained in beautiful crystals. A solution of 
this substance, mixed with dilute sulphuric acid, furnishes sulphate of soda, 
sulphuretted hydrogen, and pentasulphide of antimony, which falls as a 
golden-yellow flocculent precipitate. 

Antimonetted hydrogen. — A compound of antimony and hydrogen exists, 
out has not been isolated ; when zinc is put into a solution of teroxide of 
antimony, and sulphuric acid added, part of the hydrogen combines with the 
25 



200 TELLURIUM. 

antimony. This gas burns with a greenish flame, giving rise to white fumej 
of teroxide of antimony. When the gas is conducted through a red-hot glasa 
tube of narrow dimensions, or burned with a limited supply of air, such aa 
is the case when a cold porcelain surface is pressed into the flame, metallio 
antimony is deposited. 

The few salts of antimony soluble in water are amply characterized by 
the orange or brick-red precipitate with sulphuretted hydrogen, which is 
soluble in solution of sulphide of ammonium, and again precipitated by an 
acid. 

Besides its application to medicine, antimony is of great importance in the 
arts of life, inasmuch as it forms with lead type-metal. This alloy expands 
at the moment of solidifying, and takes an exceedingly sharp impression of 
the mould. It is remarkable that both its constituents shrink under similar 
circumstances, and make very bad castings. Tersulphide of antimony enters 
into the comnosition of the blue signal-light, used at sea. 1 

TELLURIUM. 

This metal, or semi-metal, is of very rare occurrence ; it is found in a few 
scarce minerals in association with silver, lead, and bismuth, apparently 
replacing sulphur, and is most easily extracted from the sulpho-telluride of 
bismuth of Chemnitz, in Hungary. The finely powdered ore is mixed with 
an equal weight of dry carbonate of soda, the mixture made into a paste 
with oil, and heated to whiteness in a closely covered crucible. Telluride 
and sulphide of sodium are produced, and metallic bismuth set free. The 
fused mass is dissolved in water and the solution freely exposed to the air, 
when the sodium and sulphur oxidize to caustic soda and hyposulphite of 
soda, while the tellurium separates in the metallic state. Tellurium has the 
colour and lustre of silver ; by fusion and slow cooling it may be made to 
exhibit the form of rhombohedral crystals similar to those of antimony and 
arsenic. It is brittle, and a comparatively bad conductor of heat and elec- 
tricity ; it has a density of 6-26, melts at a little below red-heat, and vola- 
tilizes at a higher temperature. Tellurium burns when heated in the air, 
and is oxidized by nitric acid. Two compounds of this substance with 
oxygen are known, having acid properties ; the} T much resemble the acids 
of arsenic. 

The equivalent of tellurium is 64-2; its symbol is Te. 

Tellurous acid, Te0 2 . — This is obtained by burning tellurium in the air, 
or by heating it in fine powder with nitric acid of 1-25 specific gravity; a 
solution is rapidly formed, from which white anhydrous octahedral crystals 
of tellurous acid are deposited on standing. The acid is fusible at a red- 
heat, and slightly volatile at a higher temperature ; it is but feebly soluble 
in water or acids, easily dissolved by alkalis, and reduced when heated with 
carbon or hydrogen. A hydrate of tellurous acid is thrown down wheu 
tellurite of potassa is mixed with a slight excess of nitric acid; it is a white 
powder, soluble to a certain extent in water, and reddens litmus. 

Telluric acid, Te0 3 . — Equal parts of tellurous acid and carbonate of 
soda are fused, and the product dissolved in water; a little hydrate of soda 
is added, and a stream of chlorine passed through the solution. The liquid 
is next saturated with ammonia, and mixed with solution of chloride of 
barium, by which a white insoluble precipitate of tellurite of baryta is thrown 
down. This is washed and digested with a quarter of its weight of sulphuric 

* Blue or Bengal light: — 

Dry nitrate of potassa 6 parts. 

Sulphur 2 " 

Tersulphide of antimony , 1 " 

All In fine powder and intimately mixed. 



ARSENIC. 291 

acid, diluted with water. The filtered solution gives, on evaporation in the 
air, large crystals of telluric acid. 

Teiiaric acid is freely, although slowly, soluble in water ; it has a metallic 
taste, and reddens litmus-paper. When the crystals are strongly heated, 
they lose water, and yield anhydrous acid, which is then insoluble in water, 
and eYen in a boiling alkaline liquid. At the temperature of ignition, telluric 
acid loses oxygen, and passes into tellurous acid. The salts of the alkalis 
are soluble, but do not crystallize ; those of the earths are nearly, or quite, 
insoluble. 

There are two chlorides of tellurium, and also a hydride, which closely 
resembles sulphuretted hydrogen. 

ARSENIC. 

Arsenic is sometimes found native ; it occurs in considerable quantity as a 
constituent of many minerals, combined with metals, sulphur and oxj'gen. 
In the oxidized state it has been found in very minute quantity in a great 
many mineral waters. The largest proportion is derived from the roasting 
of natural arsenides of iron, nickel, and cobalt; the operation is conducted 
in a reverberatory furnace, and the volatile products condensed in a long and 
nearly horizontal chimney, or in a kind of tower of brickwork, divided into 
numerous chambers. The crude arsenious acid thus produced is purified by 
sublimation, and then heated with charcoal in a retort ; the metal is reduced, 
and readily sublimes. 

Arsenic has a steel-grey colour, and high metallic lustre ; it is crystalline 
and very brittle ; it tarnishes in the air, but may be preserved unchanged in 
pure water. Its density is 5-7 to 5-9. When heated, it volatilizes without 
fusion, and, if air be present, oxidizes to arsenious acid. The vapour has 
the odour of garlic. This substance combines with metals in the same 
manner as sulphur and phosphorus, which it resembles, especially the latter, 
in many respects. With oxygen it unites in two proportions, giving rise to 
arsenious and arsenic acids. There is no basic oxide of arsenic. 

The equivalent of arsenic is 75 ; it symbol is As. 

Arsenious acid; white oxide of arsenic; As0 8 . — The origin of this 
substance is mentioned above. It is commonly met with in the form of a 
heavy, white, glassy-looking substance, with smooth conchoidal fracture, 
which has evidently undergone fusion. When freshly prepared, it is often 
transparent, but by keeping becomes opaque, at the same time slightly 
diminishing in density, and acquiring a greater degree of solubility in water. 
100 parts of that liquid dissolve at 212° (100°C), about 11-5 parts of the 
opaque variety ; the largest portion separates, however, on cooling, leaving 
about 3 parts dissolved ; the solution feebly reddens litmus. Cold water, 
agitated with powdered arsenious acid, takes up a still smaller quantity. 
Alkalis dissolve this substance freely, forming arsenites ; also compounds 
with ammonia, baryta, strontia, lime, magnesia, and oxide of manganese, 
have been formed ; it is also easily soluble in hot hydrochloric acid. The 
vapour of arsenious acid is colourless and inodorous ; it crystallizes on solidi- 
fying in brilliant transparent octahedrons. The acid itself has a feeble 
sweetish and astringent taste, and is a most fearful poison. 1 

1 The best antidote for arsenious acid is the hydrate of the red oxide of iron. In its recently 
precipitated gelatinous condition, it is most active. It acts by forming an insoluble arseniate 
of the protoxide of iron; for the peroxide is reduced to protoxide by losing oxygen, which, 
passing to the arsenious acid, forms arsenic acid. This change is represented by the following 
formula, 

2 Fe20s and As03 = 4 FeO + AsOs. 

The hydrate is incapable of decomposing the arsenites. The red oxide, to act as an antidote 
to tho arsenical salts, requires to be combined with an acid, which may separate the base, and 



292 ARSENIC. 

Arsenic acid, As0 5 . — Powdered arsenious acid is dissolved in hot hydro- 
chloric acid, and oxidized by the addition of nitric acid, the latter being 
added as long as red vapours are produced ; the whole is then cautiously 
evaporated to complete dryness. The acid thus produced is white and an- 
hydrous. Put into water, it slowly but completely dissolves, giving a highly 
acid solution, which, on being evaporated to a syrupy consistence, deposits, 
after a time, hydrated crystals of arsenic acid. When strongly heated, it is 
decomposed into arsenious acid and oxygen gas. 

This substance is a very powerful acid, comparable with phosphoric, which 
it resembles in the closest manner, forming salts strictly isomorphous with 
the corresponding phosphates ; it is also tribasic. An arsenate of soda, 
2NaO,HO,As0 5 -}- 24HO, indistinguishable in appearance from common phos- 
phate of soda, may be prepared by adding the carbonate to a solution of ar- 
senic acid, until an alkaline reaction is apparent, and then evaporating. 
This salt also crystallizes with 14 equivalents of water. Another arsenate, 
3NaO,As0 5 -f- 24HO, is produced when carbonate of soda in excess is fused 
with arsenic acid, or when the preceding salt is mixed with caustic soda. A 
third, NaO,2IIO,As0 5 -}-2HO, is made by substituting an excess of arsenic 
acid for the solution of alkali. The alkaline arsenates which contain basic 
water lose the latter at a red-heat, but unlike the phosphates, recover it 
when again dissolved. 1 The salts of the alkalis are soluble in water ; those 
of the earths and other metallic oxides are insoluble, but are dissolved by 
acids. The precipitate with nitrate of silver is highly characteristic of arse- 
nic acid ; it is reddish-brown. 

Three Sulphides of Arsenic are known. Realgar, AsS 2 , occurs native ; 
it is formed artificially, by heating arsenic acid with the proper proportion 
of sulphur. It is an orange-red, fusible, and volatile substance, employed 
in painting and by the pyrotechnist in making white-fire. Orpiment, AsS 3 , 
which is also a natural product of the mineral kingdom, is made by fusing 
arsenic acid with excess of sulphur, or by precipitating a solution of the acid 
by sulphuretted hydrogen. It is a golden-yellow crystalline substance, fusi- 
ble and volatile by heat. A higher sulphide, AsS 5 , corresponding to arsenic 
acid, is produced when sulphuretted hydrogen is transmitted through a solu- 
tion of arsenic acid. The solution of arsenic acid is not immediately pre- 
cipitated, the pentasulphide being deposited only after some hours' stand- 
ing. Its precipitation is considerably accelerated by ebullition. It is a 
3^ellow fusible substance, capable of sublimation. Realgar, orpiment, and 
pentasulphide of arsenic are sulphur-acids. 

Arsenic unites with chlorine, iodine, &c. The ierchloride, AsCl 3 , is formed 
by distilling a mixture of 1 part of arsenic, and 6 parts of corrosive subli- 
mate ; it is a colourless, volatile liquid, decomposed by water into arsenious 
and hydrochloric acids. The same substance is produced, with disengage- 
ment of heat and light, when powdered arsenic is thrown into chlorine gas. 
The iodide, Asl s , is formed by heating metallic arsenic with iodine; it is a 
deep red crystalline substance, capable of sublimation. The bromide and 
fluoride are both liquid. 

Arsenic also combines with hydrogen, forming a gaseous compound, AsH 3 , 
analogous to phosphoretted hydrogen. It is obtained pure by the action of 
strong hydrochloric acid on an alloy of equal parts of zinc and arsenic, and 
is produced in greater or less proportion whenever hydrogen is set free in 

then the arsenious acid and red oxide react on each other as above. The acetate of the red 
oxide is the salt used. 

Magnesia has also been recommended. In the state of recently precipitated hydrate, it acts 
on a solution of arsenious acid with nearly the same rapidity as the hydrated peroxide of 
iron. In the condition usually found in the shops, it cannot be depended on with the same 
certainty, having been too highly calcined. — R. B. 

1 Graham, Elements, p. 435. 



ARSENIC. 293 

contact with arsetiious acid. Arsenetted hydrogen is a colourless gas, of 
2-695 specific gravity, slightly soluble in water, and having the smell of gar- 
lic. It burns when kindled with a blue flame, generating aisenious acid. It 
is also decomposed by transmission through a red-hot tube. Many metallic 
solutions are precipitated by this substance. It is, when inhaled, exceed- 
ingly poisonous, even in very minute quantity. 



Arsenious acid is distinguished by characters which cannot be misunder- 
stood. 

Nitrate of silver, mixed with a solution of arsenious acid in water, occa- 
sions no precipitate, or merely a faint cloud; but if a little alkali, as a drop 
of ammonia, be added, a yellow precipitate of arsenite of silver immediately 
falls. The precipitate is exceedingly soluble in excess of ammonia ; that 
substance must, therefore, be added with great caution ; it is likewise very 
soluble in nitric acid. ' 

Sulphate of copper gives no precipitation with solution of arsenious acid, 
until the addition has been made of a little alkali, when a brilliant yellow- 
green precipitate (Scheele's green) falls, which also is very soluble in excess 
of ammonia. 

Sulphuretted hydrogen passed into a solution of arsenious acid, to which 
a few drops of hydrochloric or sulphuric acid have been added, occasions 
the production of a copious bright yellow precipitate of orpiment, which is 
dissolved with facility by ammonia, and re-precipitated by acids. 

Solid arsenious acid, heated by the blow- 
pipe in a narrow glass tube with small frag- Fig. 150. 
ments of dry charcoal, affords a sublimate 
of metallic arsenic in the shape of a bril- 
liant steel-grey metallic ring. A portion of 
this, detached by the point of a knife and 
heated in a second glass tube, with access of 
air, yields, in its turn, a sublimate of colour- 
less, transparent, octahedral crystals of ar- 
senious acid. (Fig. 150, magnified). 

All these experiments, which jointly give 
demonstrative proof of the presence of the 
substance in question, may be performed, with 
perfect precision and certainty, upon exceed- 
ingly small quantities of material. 

The detection of arsenious acid in complex 
mixtures containing organic matter and common salt, as beer, gruel, soup, 
&c, or the fluid contents of the stomach in cases of poisoning, is a very far 
more difficult problem, but one which is, unfortunately, often required to be 
solved. These organic matters interfere completely with the liquid tests, 
and render their indications worthless. Sometimes the difficulty may be 
eluded by a diligent search in the suspected liquid, and in the vessel con- 
taining it, for fragments or powder of solid arsenious acid, which, from the 
small degree of solubility, often escape solution, and from the high density 
of the substance may be found at the bottom of the vessels in which the 
fluids are contained. If anything of the kind be found, it may be washed 
by decantation with a little cold water, dried, and then reduced with char- 
coal. For the latter purpose, a small glass tube is taken, having the figure 
represented in the margin ; white German glass, free from lead, is to bo 
preferred. The arsenious acid, or what is suspected to be such, is dropped 
to the bottom, and covered with splinters or little fragments of charcoal, 
25* 




294 ARSENIC. 

Tig. 151. the tube being filled to the shoulder. The whole is gently 
heated, to expel any moisture that may be present in the char- 
coal, and the deposited water -wiped from the interior of the 
tube with bibulous paper. The narrow part of the tube con- 
taining the charcoal, from a to b, (fig. 151), is now heated by 
the blowpipe flame ; when red-hot, the tube is inclined, so that 
the bottom also may become heated. The arsenious acid, if 
present, is vaporized, and reduced by the charcoal, and a ring 
of metallic arsenic deposited on the cool part of the tube. 
To complete the experiment, the tube may be melted at a by 
the point of the flame, drawn off, and closed, and the arsenic 
oxidized to arsenious acid, by chasing it up and down by the 
heat of a small-spirit-lamp. A little water may afterwards 
be introduced, and boiled in the tube, by which the arsenious 
acid will be dissolved, and to this solution the tests of nitrate 
of silver and ammonia, sulphate of copper and ammonia, and 
sulphuretted hydrogen, may be applied. 

When the search for solid arsenious acid fails, the liquid 
itself must be examined ; a tolerably limpid solution must be 
obtained, from which the arsenic may be precipitated by 
sulphuretted hydrogen, and the orpiment collected, and reduced to the 
metallic state. It is in the first part of this operation that the chief diffi- 
culty is found ; such organic mixtures refuse to filter, or filter so slowly, 
as to render some method of acceleration indispensable. Boiling with a 
little caustic potassa or acetic acid will sometimes effect this object. The 
following is an outline of a plan, which has been found successful in a 
variety of cases, in which a very small quantity of arsenious acid had been 
purposely added to an organic mixture. Oil of vitriol, itself perfectly free 
from arsenic, is mixed with the suspected liquid, in the proportion of 
about a measured ounce to a pint, having been previously diluted with 
a little water, and the whole is boiled in a flask for half an hour, or until 
a complete separation of solid and liquid matter becomes manifest. The 
acid converts any starch that may be present into dextrin and sugar ; 
it coagulates completely albuminous substances, and casein, in the case of 
milk, and brings the whole in a very short time into a state in which filtra- 
tion is both easy and rapid. Through the filtered solution, when cold, a 
current of sulphuretted hydrogen is transmitted, and the liquid is warmed, 
to facilitate the deposition of the tersulphide, which falls in combination 
with a large quantity of organic matter, which often communicates to it a 
dirty colour. This is collected upon a small filter, and washed. It is next 
transferred to a capsule, and heated with a mixture of nitric and hydro- 
chloric acids, by which the organic impurities are in a great measure de- 
stroyed, and the arsenic oxidized to arsenic acid. The solution is evaporated 
to dryness, the soluble part taken up by dilute hydrochloric acid, and then 
the solution saturated with sulphurous acid, whereby the arsenic acid is re- 
duced to the state of arsenious acid, the sulphurous being oxidized to sul- 
phuric acid ; the solution of arsenious acid may be precipitated by sulphu- 
retted hydrogen without any difficulty. The liquid is warmed, and the pre- 
cipitate washed by decantation, and dried. It is then mixed with black-flux, 
and heated in a small glass tube, similar to that already described, with 
similar precautions ; a ring of reduced arsenic is obtained, which may be 
oxidized to arsenious acid, and farther examined. The black-flux is a mix- 
ture of carbonate of potassa and charcoal, obtained by calcining cream of 
tartar in a close crucible ; the alkali transforms the sulphide into arsenious 
acid, the charcoal subsequently effecting the deoxidation. A mixture of 



ARSENIC 



295 



Fig. 152. 



anhydrous carbonate of soda and charcoal may be substituted with advan- 
tage for the common black-flux, as it is less hygroscopic. 1 

Other methods of proceeding, different in pi-inciple from the foregoing, 
have been proposed, as that of the late Mr. Marsh, which is exceedingly 
delicate. The suspected liquid is acidulated with sulphuric acid and placed 
in contact with metallic zinc ; the hydrogen reduces the arsenious acid and 
combines with the arsenic, if any be present. The gas is burned at a jet, 
and a piece of glass or porcelain held in the flame, when any admixture of 
arsenetted hydrogen is at once known by the production of a brilliant black 
metallic spot of reduced arsenic on the porcelain. 

It has been observed (page 290) that antimonetted hydrogen gives a simi- 
lar result. In order to distinguish the two substances, the gas may be 
passed into a solution of nitrate of silver. Both gases give rise to a black 
precipitate, which in the case of antimonetted hydrogen consists of antimo- 
nide of silver, Ag 3 Sb, whilst it is pure silver in the case of arsenetted hy- 
drogen, the arsenic being then converted into arsenious acid, which combines? 
with a portion of oxide of silver. The arsenite of 
silver remains dissolved in the nitric acid which is li- 
berated by the precipitation of the silver, and may 
be thrown down with its characteristic yellow colour 
by adding ammonia to the liquid filtered off from the 
black precipitate. 

A convenient form of Marsh's instrument is that 
shown in fig. 152, it consists of a bent tube, having 
two bulbs blown upon it, fitted with a stop-cock and 
narrow jet. Slips of zinc are put into the lower bulb, 
which is afterwards filled with the liquid to be ex- 
amined. On replacing the stop-cock, closed, the gas 
collects and forces the fluid into the upper bulb, 
which then acts by its hydrostatic pressure and ex- 
pels the gas through the jet as soon as the stop-cock is 
opened. It must be borne in mind that both common 
zinc and sulphuric acid often contain traces of arsenic. 3 

A slip of copper foil boiled in the poisoned liquid, 
previously acidulated with hydrochloric acid, with- 
draws the arsenic and becomes covered with a white 
alloy. By heating the metal in a glass tube, the 
arsenic is expelled, and oxidized to arsenious acid. 




1 See a paper by the author on the detection of arsenic. Pharmaceutical Journal, i. 514. 

3 Where the amount of arsenic present is small, it becomes necessary to take advantage of 
the effects of heat, and cause the gas to pass slowly through a red-hot tube until all the zinc 
is dissolved. The reduced arsenic will be deposited on the cool part of the tube just beyond 
the heated portion. In all cases of using the above test, it is necessary to ascertain the purity 
of the zinc and acid by trial, previous to addition of the suspected liquid. — E. B. 



1196 s i l y e it 



SECTION VI. 

METALS WHOSE OXIDES ARE REDUCED BY HEAT. 



SILVER. 

Silver is found in the metallic state, in union with sulphur, and also ag 
chloride and bromide. Among the principal silver mines may be mentioned 
those of the Hartz mountains iu Germany, of Kongsberg in Norway, and, 
more particularly, of the Andes in both North and South America. 

The greater part of the silver of commerce is extracted from ores so poor 
as to render any process of smelting or fusion inapplicable, even "where fuel 
could be obtained, and this is often difficult to be procured. Recourse, there- 
fore, is had to another method, that of amalgamation, founded on the easy 
solubility of silver and many other metals in metallic mercury. 

The amalgamation-process, as conducted in Germany, differs somewhat 
from that in use in America. The ore is crushed to powder, mixed with a 
quantity of common salt, and roasted at a low red-heat in a suitable furnace, 
by which treatment any sulphide of silver it may contain is converted into 
chloride. The mixture of earthy matter, oxides of iron, copper, soluble 
salts, chloride of silver, and metallic silver, is sifted and put into large bar- 
rels, made to revolve on axes, with a quantity of water and scraps of iron, 
and the whole agitated together for some time, during which the iron reduces 
the chloride of silver to the state of metal. A certain proportion of mer- 
cury is then introduced, and the agitation repeated ; the mercury dissolves 
out the silver, together with gold, if there be any, metallic copper, and other 
substances, forming a fluid amalgam easily separable from the thin mud of 
earthy matter by subsidence and washing. This amalgam is strained 
through strong linen cloth, and the solid portion exposed to heat in a kind 
of retort, by which the remaining mercury is distilled off and the silver left 
behind in an impure condition. 

A considerable quantity of silver is obtained from argentiferous galena ; 
in fact, almost every specimen of native sulphide of lead will be found to 
contain traces of this metal. When the proportion rises to a certain amount 
it becomes worth extracting. The ore is reduced in the usual manner, the 
whole of the silver remaining with the lead ; the latter is then re-melted in 
a large vessel, and allowed slowly to cool until solidification commences. 
The portion which first crystallizes is nearly pure lead, the alloy with silver 
being more fusible than lead itself ; by particular management this is drained 
away, and found to contain nearly the whole of the silver. This rich mass 
is next exposed to a red-heat on the shallow hearth of a furnace, while a 
stream of air is allowed to impinge upon its surface ; oxidation takes place 
with great rapidity, the fused oxide or litharge being constantly swept from 
the metal by the blast. When the greater part of the lead has been thus 
removed, the residue is transferred to a cupel or shallow dish made of bone- 
ashes, and again heated ; the last of the lead is now oxidized, and the oxide 



SILVER. 297 

sinks in a melted state into the porous vessel, while the silver, almost che- 
mically pure, and exhibiting a brilliant surface, remains behind. 

Pure silver may be easily obtained. The metal is dissolved in nitric acid; 
if it contains copper, the solution will have a blue tint; gold will remain un- 
dissolved as a black powder. The solution is mixed with hj^drochloric acid 
or with common salt, and the white, insoluble curdy precipitate of chloride 
of silver washed and dried. This is then mixed with about twice its weight 
of anhydrous carbonate of soda, and the mixture, placed in an earthen cru- 
cible, gradually raised to a temperature approaching whiteness, during 
which the carbonate of soda and the chloride react upon each other, carbonic 
acid and oxygen escape, while metallic silver and chloride of sodium result ; 
the former fuses into a button at the bottom of the crucible, and is easily 
detached. 

Pure silver has a most perfect white colour, and a high degree of lustre ; 
it is exceedingly malleable and ductile, and is probably the best conductor 
both of heat and electricity known. Its specific gravity is 10-5. In hardness 
it lies between gold and copper. It melts at a bright red-heat, about 1873° 
(1023°C), according to the observations of Mr. Daniell. Silver is inalterable 
by air and moisture ; it refuses to oxidize at any temperature, but possesses 
the extraordinary faculty, already noticed in an earlier part of the work, of 
absorbing many times its volume of oxygen when strongly heated in an at- 
mosphere of that gas, or in common air. This oxygen is again disengaged 
at the moment of solidification, and gives rise to the peculiar arborescent 
appearance often remarked on the surface of masses or buttons of pure 
silver. The addition of 2 per cent, of copper is sufficient to prevent this 
absorption of oxygen. Silver oxidizes when heated with fusible siliceous 
matter, as glass, which it stains yellow or orange, from the formation of a 
silicate. It is little attacked by hydrochloric acid ; boiling oil of vitriol con- 
verts it into sulphate with evolution of sulphurous acid ; and nitric acid, 
even dilute and in the cold, dissolves it readily. The tarnishing of surfaces 
of silver exposed to the air is due to sulphuretted hydrogen, the metal having 
a strong attraction for sulphur. There are three oxides of silver, one of 
which is a powerful base isomorphous with potassa, soda, and oxide of am- 
monium. 

The equivalent of silver is 108 ; its symbol is Ag (argentum). 

Suboxide of silver, Ag 2 0. — When dry citrate of silver is heated to 212° 
(100°C) in a stream of hydrogen gas, it loses oxygen and becomes dark 
brown. The product dissolved in water, gives a dark-coloured solution con- 
taining free citric acid and citrate of the suboxide of silver. The suboxide 
is then precipitated by potassa. It is a black powder, very easily decom- 
posed, and soluble in ammonia. The solution of citrate is rendered colourless 
by heat, being resolved into a salt of the protoxide and metallic silver. 

Protoxide op silver, AgO. — Caustic potassa added to a solution of 
nitrate of silver throws down a pale-brown precipitate, which consists of 
protoxide of silver. It is very soluble in ammonia, and is dissolved also to 
a small extent by pure water; the solution is alkaline. Recently precipitated 
chloride of silver, boiled in a solution of caustic potassa of specific gravity 
1-25, according to the observation of Dr. Gregory, is converted, although 
with difficulty, into oxide of silver, which in this case is black and very dense. 
The protoxide of silver neutralizes acids completely, and forms, for the most 
part, colourless salts. It is decomposed by a red-heat, with extrication of 
oxygen, spongy metallic silver being left; the sun's rays also effect its de- 
composition to a small extent. 

Peroxide of silver. — This is a black crystalline substance which forms 
upon the positive electrode of a voltaic arrangement employed to decompose 
a solution of nitrate of silver. It is reduced by heat, evolves chlorine when 



298 SILVER. 

acted upon by hydrochloric acid, explodes when mixed with phosphorus and 
struck, and decomposes solution of ammonia with great energy and rapid 
disengagement of nitrogen gas. 

Nitrate of silver, AgO,N0 5 . — The nitrate is prepared by directly dis- 
solving silver in nitric acid and evaporating the solution to dryness, or until 
it is strong enough to crystallize on cooling. The crystals are colourless, 
transparent, anhydrous tables, soluble in an equal weight of cold, and in 
half that quantity of boiling water ; they also dissolve in alcohol. They fuse 
when heated like those of nitre, and at a higher temperature suffer decom- 
position ; the lunar caustic of the surgeon is nitrate of silver which has been 
melted and poured into a cylindrical mould. The salt blackens when exposed 
to light, more particularly if organic matters of any kind be present, and is 
frequently employed to communicate a dark stain to the hair ; it enters into 
the composition of the "indelible" ink used for marking linen. The black 
stain has been thought to be metallic silver ; it may possibly be suboxide. 
Pure nitrate of silver may be prepared from the metal alloyed with copper : 
the alloy is dissolved in nitric acid, the solution evaporated to dryness, and 
the mixed nitrates cautiously heated to fusion. A small portion of the melted 
mass is removed from time to time for examination ; it is dissolved in water, 
filtered, and ammonia added to it in excess. While any copper-salt remains 
undecomposed, the liquid will be blue, but when that no longer happens, the 
nitrate may be suffered to cool, dissolved in water, and filtered from the inso- 
luble black oxide of copper. 

Sulphate of silver, AgO,S0 3 . — The sulphate may be prepared by boil- 
ing together oil of vitriol and metallic silver, or by precipitating a concen- 
trated solution of nitrate of silver by an alkaline sulphate. It dissolves in 
88 parts of boiling water, and separates in great measure in a crystalline 
form on cooling, having but a feeble degree of solubility at a low tempera- 
ture. It forms a crystallizable compound with ammonia, freely soluble in 
water, containing AgO,S0 3 -f 2NH 3 . 

Ilyposulphatc of Silver, AgO,S 2 5 -{-HO, is a soluble crystallizable salt, 
permanent in the air. The hyposulphite is insoluble, white, and very prone 
to decomposition ; it combines with the alkaline hyposulphites, forming solu- 
ble compounds distinguished by an intensely sweet taste. The alkaline hy- 
posulphites dissolve both oxide and chloride of silver, and give rise to similar 
salts, an oxide or chloride of the alkaline metal being at the same time 
formed. Carbonate of silver is a white insoluble substance obtained by mix- 
ing solutions of nitrate of silver and of carbonate of soda. It is blackened 
and decomposed by boiling. 

Chloride of silver, AgCl. — This substance is almost invariably produced 
when a soluble salt of silver and a soluble chloride are mixed. It falls as a 
white curdy precipitate, quite insoluble in water and nitric acid, but one 
part of chloride of silver is soluble in 200 parts of hydrochloric acid when 
concentrated, and in about 600 parts when diluted with double its weight 
of water. "When heated it melts, and on cooling becomes a greyish crystal- 
line mass, which cuts like horn ; it is found native in this condition, consti- 
tuting the horn-silver of the mineralogist. Chloride of silver is decomposed 
by light both in a dry and wet state, very slowly if pure, and quickly if or- 
ganic matter be present : it is reduced also when put into water with metal- 
lic zinc or iron. It is soluble with great ease in ammonia and in a solution 
of cyanide of potassium. In practical analysis the proportion of chlorine 
or hydrochloric acid in a compound is always estimated by precipitation by 
solution of silver. The liquid is acidulated with nitric acid, and an excess 
of nitrate of silver added; the chloride is collected on a filter, or better by 
subsidence, washed, dried, and fused ; 100 parts correspend to 24-7 of chlo- 
rine, or 25-43 of hydrochloric acid. 



GOLD. 299 

Iodide of silver, Agl. — The iodide is a pale yellow insoluble precipitate 
produced by adding nitrate of silver to iodide of potassium; it is insoluble, 
or nearly so, in ammonia, and forms an exception to the silver-salts in gene- 
ral in this respect. The bromide of silver very closely resembles the 
chloride. 

Sulphide of silver, AgS. — This is a soft, grey, and somewhat malleablo 
substance, found native in a crystallized state, and easily produced by melt- 
ing together its constituents, or by precipitating a solution of silver by sul- 
phuretted hydrogen. It is a strong sulphur-base, and combines with the 
sulphides of antimony and arsenic : examples of such compounds are found 
in the beautiful minerals dark and light red silver ore. 

Ammonia compound of silver; Berthollet's fulminating silver. — ■ 
When precipitated oxide of silver is digested in ammonia, a black substance 
is. produced, possessing exceedingly dangerous explosive properties. It 
explodes while moist when rubbed with a hard body, but when dry the touch 
of a feather is sufficient. The ammonia retains some of this substance in 
solution, and deposits it in small crystals by spontaneous evaporation. A 
similar compound containing oxide of gold exists. It is easy to understand 
the reason why these bodies are subject to such violent and sudden decom- 
position by the slightest cause, on the supposition that they contain an oxide 
of an easily reducible metal and ammonia. ; the attraction between the two 
constituents of the substance is very feeble, while that between the oxygen 
of the one and the hydrogen of the other is very powerful. The explosion 
is caused by the sudden evolution of nitrogen gas and vapour of water, the 
metal being set free. 



A soluble salt of silver is perfectly characterized by the white curdy pre- 
cipitate of chloride of silver, darkening by exposure to light, and insoluble 
in hot nitric acid, which is produced by the addition of any soluble chlo- 
ride. Lead is the only metal which can be confounded with it in this re- 
spect, but chloride of lead is soluble to a great extent in boiling water, and 
is deposited in brilliant acicular crystals when the solution cools. Solutions 
of silver are reduced to the metallic state by iron, copper, mercury, and other 
metals. 

The economical uses of silver are many : it is admirable for culinary and 
other similar purposes, not being attacked in the slightest degree by any 
of the substances used for food. It is necessary, however, in these cases 
to diminish the softness of the metal by a small addition of copper. The 
standard silver of England contains 222 parts of silver and 18 parts of 
copper. 

GOLD. 

Gold, in small quantities, is a very widely diffused metal ; traces are con- 
stantly found in the iron pyrites of the more ancient rocks. It is always 
met with in the metallic state, sometimes beautifully crystallized in the cubic 
form, associated with quartz, oxide of iron, and other substances, in regular 
mineral veins. The sands of various rivers have long furnished gold derived 
from this source, and separable by a simple process of washing ; such is the 
gold-dust of commerce. When a veinstone is wrought for gold, it is stamped 
to powder, and shaken in a suitable apparatus with water and mercury ; an 
amalgam is formed, which is afterwards separated from the mixture and de- 
composed by distillation. 

The pure metal is obtained by solution in nitro-hydrochloric acid and pre- 
cipitation by a salt of protoxide of iron, which, by undergoing peroxidation, 



soo 



GOLD 



reduces the gold. The latter falls as a brown powder, which Acquires the 
metallic lustre by friction. 

Gold is a suit metal, having a beautiful yellow colour. It surpasses all 
other metals in malleability, the thinnest gold-leaf not exceeding, it is said, 
o ttott or °f an i ncn m thickness, while the gilding on the silver wire used in 
tlie manufacture of gold-lace is still thinner. It may also be drawn into very 
fine wire. Gold has a density of 19-5 ; it melts at a temperature a little 
above the fusing-point of silver. Neither air nor water aifect it in the least 
at any temperature ; the ordinary acids fail to attack it, singly. A mixture 
of nitric and hydrochloric acids dissolves gold, however, with ease, the ac- 
tive agent being the liberated chlorine. Gold forms two compounds with 
oxygen, and two corresponding compounds with chlorine, iodine, sulphur, 
&c. Both oxides refuse to unite with acids. 

The equivalent of gold is 197. Its symbol is Au (aurum). 

Protoxtde of gold, AuO. — The protoxide is produced when caustic pq- 
tassa in solution is poured upon the protochloride. It is a green powder, 
partly soluble in the alkaline liquid ; the solution rapidly decomposes into 
metallic gold, which subsides, and into teroxide, which remains dissolved. 

Teroxide of gold ; auric acid ; Au0 3 . — When magnesia is added to the 
terchloride of gold, and the sparingly soluble aurate of that base well washed 
and digested with nitric acid, the teroxide is left as an insoluble reddish- 
yellow powder, which, when dry, becomes chestnut-brown. It is easily re- 
duced by heat, and also by mere exposure to light ; it is insoluble in oxygen 
acids with the exception of strong nitric acid, insoluble in hydrofluoric acid, 
easily dissolved by hydrochloric and hydrobromic acids. Alkalis dissolve it 
freely ; indeed, the acid properties of this substance are very strongly 
marked ; it partially decomposes a solution of chloride of potassium when 
boiled with that liquid, potassa being produced. When digested with ammo- 
nia, it furnishes fulminating gold. 

Protochloride of gold, AuCl. — This substance is produced when the 
terchloride is evaporated to dryness and exposed to a heat of 440° (226° -6C) 
until chlorine ceases to be exhaled. It forms a yellowish-white mass, inso- 
luble in water. In contact with that liquid it is decomposed slowly in the 
cold, and rapidly by the aid of heat, into metallic gold and terchloride. 

Terchloride of gold, AuC1 3 . — This is the most important compound of 
the metal ; it is always produced when gold is dissolved in nitro-hydrochloric 
acid. The deep yellow solution thus obtained yields, by evaporation, yellow 
crystals of the double chloride of gold and hydrogen ; when this is cautiously 
heated, hydrochloric acid is expelled, and the residue, on cooling, solidifies 
to a red crystalline mass of terchloride of gold, very deliquescent, and so- 
luble in water, alcohol, and ether. The terchloride of gold combines with a 
number of metallic chlorides, forming a series of double salts, of which the 
general formula in the anhydrous state is MCl-f-AuCl 3 .M representing an 
equivalent of the second metal. These compounds are mostly yellow when 
in crystals, and red when deprived of water. 

A mixture of terchloride of gold with excess of bicarbonate of potassa or 
soda is used for gilding small ornamental articles of copper; these are 
cleaned by dilute nitric acid, and then boiled in the mixture for some time, 
by which means they acquire a thin but perfect coating of reduced gold. 

The other compounds of gold are of very little importance. 



The presence of this metal in solution may be known by the brown pre- 
cipitate with sulphate of protoxide of iron, fusible before the blowpipe into 
a bead of gold ; and by the purple compound formed when the terchloride 
of gold is added to a solution of protochloride of tin. 



MERCURY, OR QUICKSILVER. 301 

Gold intended for coin, and most other purposes, is always alloyed with a 
certain proportion of silver or copper, to increase its hardness and durability ; 
the first named metal confers a pale greenish colour. English standard gold 
contains T \ of alloy, now always copper. Gold-leaf is made by rolling out 
plates of p"are gold as thin as possible, and then beating them between folds 
of membrane by a heavy hammer, until the requisite degree of tenuity has 
been reached. The ler-.f is made to adhere to wood, &c, by size or varnish. 

Gilding on copper has very generally been performed by dipping the arti- 
cles into a solution of nitrate of mercury, and then shaking them with a 
small lump of a soft amalgam of gold with that metal, which thus becomes 
spread over their surfaces ; the articles are subsequently heated to expel the 
mercury and then burnished. Gilding on steel is done either by applying a 
solution of terchloride of gold, in ether, or by roughening the surface of the 
metal, heating it, and applying gold-leaf, with a burnisher. Gilding by 
electrolysis — an elegant and simple method, now rapidly superseding many 
of the others — has already been noticed. The solution usually employed is 
obtained by dissolving oxide or cyanide of gold in a solution of cyanide of 
potassium. 1 

MERCURY, OR QUICKSILVER. 

This very remai'kable metal has been known from an early period, and, 
perhaps more than, all others, has excited the attention and curiosity of ex- 
perimenters, by reason of its peculiar physical properties. Mercury is of 
great importance in several of the arts, and enters into the composition of 
many valuable medicaments. 

Metallic mercury is occasionally met with in globules disseminated through 
the native sulphide, which is the ordinary ore. This latter substance, 
sometimes called cinnabar, is found in considerable quantity in several 
localities, of which the most celebrated are Almaden in New Castile and 
Idria in Carniola. Only recently it has been discovered in great abundance, 
and of remarkable purity, in California. The metal is obtained by heating 
the sulphide in an iron retort with lime or scraps of iron, or by roasting it 
in a furnace, and conducting the vapours into a large chamber, where the 
mercury is condensed, while the sulphurous acid is allowed to escape. 
Mercury is imported into this country in bottles of hammered iron, contain- 
ing seventy-five pounds each, and in a state of considerable purity. When 
purchased in smaller quantities, it is sometimes found adulterated with tin 
and lead, which metals it dissolves to some extent without much loss of 
fluidity. Such admixture may be known by the foul surface the mercury 
exhibits when shaken in a bottle containing air, and by the globules, when 
made to roll upon the table, having a train or tail. 

Mercury has a nearly silver-white colour, and a very high degree of lustre ; 
it is liquid at all ordinary temperatures, and only solidifies when cooled to 
_ 40° (— 40°C). In this state it is soft and malleable. At 662° (350°C) it 
boils, and yields a transparent, colourless vapour, of great density. The 
metal volatilizes, however, to a sensible extent at all temperatures above 68° 
(20°C) or 70° (21°C); below this point its volatility is imperceptible. The 
volatility of mercury at the boiling heat is singularly retarded by the pre- 
sence of minute quantities of lead or zinc. The specific gravity of mercury 
at 60° (15°-5C) is 13-59 ; that of frozen mercury about 14, great contraction 
taking place in the act of solidification. 

Pure quicksilver is quite inalterable in the air at common temperatures, 
but when heated to near its boiling point it slowly absorbs oxygen, and be- 
comes converted into a crystalline dark red powder, which is the highest 

1 Messrs. Elkiagton, Application of Electro-Metallurgy to the Arts. 

26 



302 MERCURY, OR QUICKSILVER. 

oxide. At a dull red-heat this oxide is again decomposed into its constituents. 
Hydrochloric acid has little or no action on mercury, and the same may ho 
said of sulphuric acid in a diluted state ; when the latter is concentrated and 
boiling hot, it oxidizes the metal, converting it into sulphate of the red oxide, 
with evolution of sulphurous acid. Nitric acid, even dilute and in the cold, 
dissolves mercury freely, with an evolution of binoxide of nitrogen. 

Mercury combines with oxygen in two proportions, forming a grey and a 
red oxide, both of which are salifiable. As the salts of the red oxide are 
the most stable and permanent, that substance may be regargded as the true 
protoxide, instead of the grey oxide, to which the term has formerly been 
applied. Until, however, isomorphous relations connecting mercury with 
the other metals shall be established, the constitution of the two oxides 
and that of the corresponding chlorides, iodides, &c, must remain somewhat 
unsettled. 1 

The equivalent of mercury on the above supposition, will be 100; its 
symbol is Hg (hydrargyrum). 

Suboxide of mercury ; grey oxide ; Hg 2 0. — The suboxide is easily 
prepared by adding caustic potassa to the nitrate of this substance, or by 
digesting calomel in solution of caustic alkali. It is a dark grey, nearly 
black, heavy powder, insoluble in water. It is slowly decomposed by the 
action of light into metallic mercury and red oxide. The preparations known 
in pharmacy by the names blue pill, grey ointment, mercury with chalk, &c, 
often supposed to owe their efficacy to this substance, merely contain the 
finely divided metal. 

Protoxide of mercury; red oxide; HgO. — There are numerous methods 
by which this method may be obtained ; the following may be cited as the 
most important: — (1) By exposing mercury in a glass flask, with a long- 
narrow neck, for several weeks to a temperature approaching 600° (315° -5C) ; 
the product has a dark red colour and is highly crystalline ; it is the red 
p-ecipitate of the old writers. (2) By cautiously heating any of the nitrates 
of either oxide to complete decomposition, when the acid is decomposed and 
expelled, oxidizing the metal to a maximum, if it happen to be in the con- 
dition of a suboxide. The product is in this case also crystalline and very 
dense, but has a much paler colour than the preceding ; while hot it is nearly 
black. It is by this method that the oxide is generally prepared ; it is apt 
to contain undecomposed nitrate, which may be discovered by strongly 
heating a portion in a test-tube : if red fumes are produced or the odour of 
nitrous acid exhaled, the oxide has been insufficiently heated in the process 
of manufacture. (3) By adding caustic potassa in excess to a solution of 
corrosive sublimate, by which a bright yellow precipitate of oxide is thrown 
down, which only differs from the foregoing preparations in being destitute 
of crystalline texture and much more minutely divided. 2 It must be well 
washed and dried. 

Red oxide of mercury is slightly soluble in water, communicating to the 
latter an alkaline reaction and metallic taste ; it is highly poisonous. When 
strongly heated, it is decomposed, as before observed, into metallic mercury 
and oxygen gas. 

Nitrates of thf oxides of mercury. — Nitric acid varies in its action 
upon mercury, according to the temperature. When cold and somewhat 
diluted, only salts of the grey oxide are formed, and these are neutral or 

4 By referring to cyanogen, it will be perceived that when the equivalent of mercury is 
considered to be 100, the constitution of the cyanide of mercury is analogous to the other 
metallic cyanides, but when taken at 200, it Lecomcs a bieyanide, and then differs from all 
others.— R. 13. 

a This precipitate is considered by Shauffner to be a hydrate. HgO,3HO, for by exposure ic 
the temperature of 392°, it loses water amounting to over 20 per cent, of its weight. — R. B. 



MERCURY, OR QUICKSILVER. 303 

"basic (*. e. -with excess of oxide), as the acid or the metal happens to be in 
excess. When, on the contrary, the nitric acid is concentrated and hot, the 
mercury is raised to its highest state of oxidation, and a salt of the red oxide 
produced. Both classes of salts are apt to be decomposed by a large 
quantity of water, giving rise to insoluble, or sparingly soluble, compounds 
containing an excess of base. 

Neutral nitrate of the suboxide, Hg 2 0,NO. -J-2HO, forms large colourless 
crystals, soluble in a small quantity of water without decomposition ; it is 
made by dissolving mercury in an excess of cold dilute nitric acid. 

When excess of mercury has been employed, a finely crystallized basic 
salt is, after some time, deposited, containing 3Hg 2 0,2N0 5 -f-3HO ; this is 
also decomposed by water. The two salts are easily distinguished when 
rubbed in a mortar with a little chloride of sodium ; the neutral compound 
gives nitrate of soda and calomel ; the basic salt, nitrate of soda and a black 
compound of calomel with oxide of mercury. A black substance, called 
Hahnemann's soluble mercury, is produced when ammonia in small quantity 
is dropped into a solution of the nitrate of the suboxide ; it contains 3Hg 2 0, 
N0 5 -j-NH 3 , or, according to Sir R. Kane, 2HgO,N0 5 -j-NH 3 ; the composition 
of this preparation evidently varies according to the temperature and the 
concentration of the solutions. 

Nitrates of the Protoxide [Red Oxide) of Mercury. — By dissolving red oxide 
of mercury in excess of nitric acid and evaporating gently, a syrupy liquid 
is obtained, which, enclosed in a bell-jar over lime or sulphuric acid, de- 
posits voluminous crystals and crystalline crusts. The crystals and crusts 
have the same composition, 2(HgO,N0 5 )-j-HO. The same substance is de- 
posited from the syrupy liquid as a crystalline powder by dropping it into 
concentrated nitric acid. The syrupy liquid itself appears to be a definite 
compound containing HgO,N0 5 -(-2HO. By saturating hot dilute nitric acid 
with the red oxide, a salt is obtained on cooling which crystallizes in needles, 
permanent in the air, containing 2HgO,N0 5 -(- HO. The preceding crystal- 
lized salts are decomposed by water, with production of compounds more and 
more basic as the washing is prolonged or the temperature of the water 
raised. The nitrates of the protoxide of mercury combine with ammonia. 

Sulphate of the Suboxide of Mercury, Hg 2 0,S0 3 , falls as a white crystalline 
powder when sulphuric acid is added to a solution of the nitrate of the sub- 
oxide ; it is but slightly soluble in water. Sulphate of the protoxide, HgO, 
S0 3 , is readily prepared by boiling together oil of vitriol and metallic mer- 
cury until the latter is wholly converted into a heavy white crystalline pow- 
der, which is the salt in question ; the excess of acid is then removed by 
evaporation, carried to perfect dryness. Equal weights of acid and metal 
may be conveniently employed. "Water decomposes the sulphate, dissolving 
out an acid salt and leaving an insoluble, yellow, basic compound, formerly 
called turpeth or turbith mineral, containing, according to Kane's analysis, 
3HgO,S0 3 . Long-continued washing with hot water entirely removes the 
remaining acid, and leaving pure protoxide of mercury. 

Subchloride of mercury ; calomel ; Hg 2 Cl. — This very importont sub- 
stance may be easily and well prepared by pouring a solution of the nitrate of 
the suboxide into a large excess of dilute solution of common salt. It falls 
as a dense white precipitate, quite insoluble in water ; it must be thoroughly 
washed with boiling distilled water, and dried. Calomel is generally pro- 
cured by another and more complex process. Dry sulphate of the red oxide 
is rubbed in a mortar with as much metallic mercury as it already contains, 
and a quantity of common salt, until the globules disappear, and an uniform 
mixture has been produced. This is subjected to sublimation, the vapour of 
the calomel being carried into an atmosphere of steam, or into a chamber 
containing air ; it is thus condensed in a minutely-divided ?tate, and the la- 




304 MERCURY, OR QUICKSILVER. 

borious process of pulverization of the sublimed mass avoided. The reaction 

is thus explained: 1 — 

f 1 eq. mercury^ Calomel, Hg a Cl. 

1 eq. sulphate! 1 eq. oxygen 
of mercury j 1 eq. sul- 
L phuric acid 

1 eq. metallic mercury 

1 eq. common ^ 1 eq. chlorine 

salt I 1 eq. sodium - -^ Sulphate of soda. 

Pure calomel is a heavy, white, insoluble, tasteless powder; it rises in 
vapour at a temperature below redness, and is obtained by ordinary subli- 
mation as a yellowish-white crystalline mass. It is as insoluble in cold di- 
luted nitric acid as the chloride of silver ; boiling-hot strong nitric acid oxi- 
dizes and dissolves it. Calomel is instantly decomposed by an alkali, or by 
lime-water, with production of sub-oxide. It is sometimes apt to contain a 
little chloride, which would be a very dangerous contamination in calomel 
employed for medical purposes. This is easily discovered by boiling with 
water, filtering the liquid, and adding caustic potassa. Any corrosive sub- 
limate is indicated by a yellow precipitate. 

Protochloride of mercury ; corrosive sublimate ; HgCl. — The chlo- 
ride may be obtained by several different processes. (1) When metallic 
mercury is heated in chlorine gas, it takes fire and burns, producing this 
substance. (2) It may be made by dissolving the red oxide in hot hydro- 
chloric acid, when crystals of corrosive sublimate separate on cooling. (8) 
Or, more economically, by subliming a mixture of equal parts of sulphate of 
the red oxide of mercury and dry common salt ; and this is the plan gene- 
rally followed. The decomposition is thus easily explained : a — 

f 1 eq. mercury -^ Corrosive sublimate. 

1 eq. sulphate of j 1 eq. oxygen 
mercury j 1 eq. sul- \ 

I phuric acid j 

- ,, f 1 eq. chlorine "" 

1 eq. common salt j x £ g()dium H^ Sulphate of goda> 

The sublimed protochloride forms a white, transparent, crystalline mass, 
of great density ; it melts at 509° (265°C), and boils and volatilizes at a 
somewhat higher temperature. It is soluble in 16 parts of cold and 3 of 
boiling water, and crystallizes from a hot solution in long white prisms. Al- 
cohol and ether also dissolves it with facility ; the latter even withdraws it 
from a watery solution. Chloride of mercury combines with a great number 

1 If the grey oxide be considered as protoxide, the sulphate will be sulphate of the binox- 
»de, IlgOa, 2S03, and the decomposition will stand thus : — 

ii,^ ( 1 eq. mercury ■ _, 2 eq. calomel, IlgCl. 

1 eq sulphate S 2 \ * ^^ 

of mercury } 2 e ^ su ^ huric acidX<^^ 
1 eq. metallic mercury ^^S^^^^N. 



2 eq. common \ 2 eq. chlorine -^ ^^. 
salt { 2 eq. sodium -^ 2 eq. sulphate of soda. 

Or on the other supposition :— 

i i i „+„ „f f 1 e( l- mercury —^Bichloride of mercury. 

leq. sulphate of J 2 \ Z^^ 



mercury 1 2 eq. sulphuric acid^X^ 

,, (2 eq. chlorine '"^^^^^^^^ 
2 eq. common salt j 2 ^ eodium _^^ 2 eq. sulphate of soda. 




OR QUICKSILVER. 305 

of other metallic chlorides, forming a series of beautiful double salts, of 
which the ancient sal ahmlroth may be taken as a good example : it contains 
HgCl-f-NH 4 Cl-}-HO. Corrosive sublimate absorbs ammoniacal gas with grea* 
avidity, generating a compound supposed to contain 2HgCl-}-NH 8 . 

When excess of ammonia is added to a solution of corrosive sublimate, p 
white insoluble substance is thrown down, long known under the name of 
while precipitate. Sir Robert Kane, who has devoted much attention to the 
salts of mercury, represents this white precipitate as a double amide and 
chloride of mercury, or HgCl-j-HgNH 2 , 2 equivalents of chloride of mercury 
and 1 of ammonia, yielding 1 equivalent of the new body and 1 of hydro- 
chloric acid. A corresponding black compound, Hg 2 Cl-f-HgNH 2 , is produced 
when ammonia is digested with calomel, which must be carefully distin- 
guished from the suboxide. 

Several compounds of protochloride of mercury with protoxide of mercury 
also exist. These are produced by several processes, as when an alkaline 
carbonate or bicarbonate is added in varying proportions to a solution of 
corrosive sublimate. They differ greatly in colour and physical character, 
and are mostly decomposed by water. 

Corrosive sublimate forms insoluble compounds with many of the azotized 
organic principles, as albumin, &c. It is perhaps to this property that its 
great antiseptic virtues are due. Animal and vegetable substances are pre- 
served by it from decay, as in Mr. Kyan's method of preserving timber and 
cordage. Albumin is on this account an excellent antidote to corrosive sub- 
limate in cases of poisoning. 

Subiodide or mercury, Hg 2 T. — The subiodide is formed when a solution 
of iodide of potassium is added to nitrate of the suboxide of mercury; it 
separates as a dirty yellow, insoluble precipitate, with a cast of green. It 
may be prepared by rubbing together in a mortar mercury and iodine in the 
proportion of 2 equivalents of the former to 1 of the latter, the mixture being 
moistened from time to time with a little alcohol. 

Protiodide of mercury, Hgl. — When solution of iodide of potassium is 
mixed with protochloride of mercur}^, a precipitate falls, which is at first 
yellow, but in a few moments changes to a most brilliant scarlet, which colour 
is retained on drying. This is the neutral iodide ; it may be made, although 
of rather duller tint, by triturating single equivalents of iodine and mercury 
with a little alcohol. When prepared by precipitation, it is better to weigh 
out the proper proportions of the two salts, as the iodide is soluble in an 
excess of either, more especially in excess of iodide of potassium. The iodide 
of mercury exhibits a very remarkable case of dimorphism, attended with 
difference of colour, the latter being red or yellow, according to the figure 
assumed. Thus, when the iodide is suddenly exposed to a high temperature, 
it becomes bright yellow throughout, and yields a copious sublimate of minute 
but brilliant yellow crystals. If in this state it be touched by a hard body, 
it instantly becomes red, and the same change happens spontaneously after 
a certain lapse of time. On the other hand, by a very slow and careful heat- 
ing, a sublimate of red crystals, having a totally different form, may be 
obtained, which are permanent. The same kind of change happens with the 
freshly precipitated iodide, as Mr. Warington has shown the yellow crystals 
first formed breaking up in the course of a few seconds from the passage of 
the salt to the red modification. 1 

Subsulphide of mercury, Hg 2 S. — The black precipitate thrown down 
from a solution of the nitrate of suboxide of mercury by sulphuretted hydro- 
gen, is a subsulphide; it is decomposed by heat into metallic mercury and 
neutral sulphide. 

1 Memoirs of Chemical Society of London, i. 85. 
26* 



™i 



306 MERCURY, OR QUICKSILVER. 

Sulphide of mercury ; artificial cinnabar ; vermilion ; HgS. — Sul- 
phuretted hydrogen gas causes a precipitate of a white colour when passed 
in small quantity into a solution of corrosive sublimate or nitrate of the red 
oxide ; this is a combination of sulphide with the salt itself. An excess of 
the gas converts the whole into sulphide, the colour at the same time chang- 
ing to black. When this black sulphide is sublimed, it becomes dark red 
and crystalline, but undergoes no change of composition ; it is then cinnabar. 
The sulphide is most easily prepared by subliming an intimate mixture of 6 
parts of mercury and 1 of sulphur, and reducing to a very fine powder the 
resulting cinnabar, the beauty of the tint depending much upon the extent 
to which division is carried. The red or crystalline sulphide may also be 
formed directly, without sublimation, by heating the black precipitated sub- 
stance in a solution of pentasulphide of potassium ; the sulphide of mercury 
is in fact soluble to a certain extent in the alkaline sulphides, and forms with 
them crystallizable compounds. 

When vermilion is heated in the air, it yields metallic mercury and sul- 
phurous acid ; it resists the action both of caustic alkali in solution, and of 
strong mineral acids, even nitric, and is only attacked by aqua regia. 



When protoxide of mercury is put into a large excess of pure caustic 
ammonia, a compound is obtained, the colour of which varies with the statu 
of the oxide. If the latter be amorphous, it is pale yellow; if crystalline, 
then the action of the ammonia is much less energetic, and the product 
darker in colour. This substance possesses very extraordinary properties, 
those, namely, of a most powerful base, and probably belongs to the same 
class as the compound bases containing platinum, described under that 
metal. The body in question bears a temperature of 260° (126° -5C), with- 
out decomposition, becoming brown and anhydrous by the loss of 3 equiva- 
lents of water. In this state it contains NH 2 Hg 4 3 =NH 2 Hg 2 0-f 2HgO or 
NHg 4 0-f-2HO. It is insoluble in water, alcohol, and ammonia; cold solu- 
tion of potassa has no action on the hydrate, but at a boiling heat some 
ammonia is disengaged. The anhydrous base is only acted on by hydrate 
of potassa in fusion. It combines directly and energetically with acids, form- 
ing well-defined compounds; it absorbs carbonic acid with avidity from the 
air, like baryta or lime. It even decomposes ammoniacal salts by boiling, 
expelling the ammonia afid combining with the acid. 1 



The salts of mercury are all volatilized or decomposed by a temperature 
of ignition ; those which fail to yield the metal by simple heating may in all 
cases be made to do so by heating in a test-tube with a little dry carbonate 
of soda. The metal is precipitated from its soluble combinations by a plate 
of copper, and also by a solution of protochloride of tin, used in excess. 
The behaviour of the protochloride and soluble salts of the red oxide with 
■•austic potassa and ammonia is also highly characteristic. 



Alloys of mercury with other metals are termed amalgams ; mercury dis- 
solves in this manner many of the metals, as gold, silver, tin, lead, &o. 
These combinations sometimes take place with considerable violence, as in 
the case of potassium, where light and heat are produced; besides this, many 
of the amalgams crystallize after a while, becoming solid. The amalgam of 



Ann. Cbim. et Pbys. 3d series xviii. 333. 



PLATINUM. 307 

tin used in silvering looking-glasses, and that of silver sometimes employed 
for stopping hollow teeth, are examples. 

PLATIXU3I. 

Platinum, palladium, rhodium, iridium, ruthenium, and osmium, form a 
small group of metals, allied in some cases by properties in common, and 
still more closely by their natural association. Crude platinum, a native alloy 
of platinum, palladium, rhodium, iridium, and a little iron, occurs in grains 
and rolled masses, sometimes of tolerably large dimensions, mixed with 
gravel and transported materials, on the slope of the Ural Mountains in 
Russia, in Ceylon, and in a few other places. It has never been seen in the 
rock, which, however, is judged, from the accompanying minerals, to have 
been serpentine. It is stated to be always present in small quantities with 
native silver. 

From this substance platinum is prepared by the following process : — The 
crude metal is acted upon as far as possible by nitro-hydrochloric acid, con- 
taining an excess of hydrochloric acid, and slightly diluted with water, in 
order to dissolve as small a quantity of iridium as possible ; to the deep yel- 
lowish-red and highly acid solution thus produced sal-ammoniac is added, by 
which nearly the whole of the platinum is thrown down in the state of am- 
monio-chloride. This substance is washed with a little cold water, dried 
and heated to redness ; metallic platinum in spongy state is left. Although 
this metal cannot be fused into a compact mass by any furnace-heat, yet the 
same object may be accomplished by taking advantage of its property of 
welding, like iron, at a very high temperature. The spongy platinum is 
made into a thin uniform paste with water, introduced into a slightly conical 
mould of brass, and subjected to a graduated pressure, by which the water 
is squeezed out, and the mass rendered at length sufficiently solid to bear 
handling. It is then dried, very carefully heated to whiteness, and ham- 
mered, or subjected to powerful pressure by suitable means. If this opera- 
tion has been properly conducted, the platinum will now be in a state to bear 
forging into a bar, which can afterwards be rolled into plates, or drawn into 
wire, at pleasure. 

Platinum is in point of colour a little whiter than iron ; it is exceedingly 
malleable and ductile, both hot and cold, and is very infusible, melting only 
before the oxy-hydrogen blowpipe. It is the (except Iridium) heaviest sub- 
stance known, its specific gravity being 21-5. Neither air, moisture, nor the 
ordinary acids attack platinum in the slightest degree at any temperature ; 
hence its high value in the construction of chemical vessels. It is dissolved 
by aqua regia, and superficially oxidized by fused hydrate of potassa, which 
enters into combination with the oxide. 

The remarkable property of the spongy metal to determine the union of 
oxygen and hydrogen has been already noticed. There is a still more curious 
state in which platinum can be obtained, that of platinum-black, where the 
division is pushed much farther. It is easily prepared by boiling a solution 
of bichloride of platinum to which an excess of carbonate of soda and a quan- 
tity of sugar have been added, until the precipitate formed after a little time 
becomes perfectly black, and the supernatant liquid colourless. The black 
powder is collected on a filter, washed, and dried by gentle heat. This sub- 
stance appears to possess the property of condensing gases, more especially 
oxygen, into its pores to a very great extent ; when placed in contact with a 
solution of formic acid, it converts the latter, with copious effervescence, into 
carbonic acid ; alcohol, dropped on the platinum-black, becomes changed by 
oxidation to acetic acid, the rise of temperature being often sufficiently greut 
to cause inflammation. "When exposed to a red-heat, the black substance 
shrinks in volume, assumes the appearance of common spongy platinum, aud 



S08 PLATINU M . 

loses these peculiarities, -which are no doubt the result of its excessively com- 
minuted state. Platinum forms two compounds with oxygen, chlorine, &c. 
The equivalent of platinum is 98-7. '' Its symbol is Pt. 

Protoxide of platinum, PtO. — When protochloride of platinum is di- 
gested with caustic potassa, a black powder, soluble in excess of alkali, is pro- 
duced : this is the protoxide. It is soluble in acids with brown colour, and 
the solutions are not precipitated by sal-ammoniac. When binoxide of pla- 
tinum is heated with solution of oxalic acid, it is reduced to protoxide, which 
remains dissolved. The liquid has a dark blue colour, and deposits fine cop- 
per-red needles of oxalate of the protoxide of platinum. 

Binoxide of platinum, Pt0 2 . — This is best prepared by adding nitrate 
of baryta to sulphate of the binoxide of platinum ; sulphate of baryta and 
nitrate of the binoxide are produced. From the latter, caustic soda precipi- 
tates one-half of the binoxide of platinum. The sulphate is itself obtained 
by acting with strong nitric acid upon the bisulphide of platinum, which falls 
as a black powder when a solution of bichloride is dropped into sulphide of 
potassium. The hydrate of the binoxide is a bulky brown powder, which, 
when gently heated, becomes black and anhj'drous. It may also be formed 
by boiling bichloride of platinum with a great excess of caustic soda, and 
then adding acetic acid. It dissolves in acids, and also combines with bases ; 
the salts have a yellow or red tint, and a great disposition to unite with salts 
of the alkalis and alkaline earths, giving rise to a series of double compounds, 
which are not precipitated by excess of alkali. A combination of binoxide 
of platinum with ammonia exists, which is explosive. Both oxides of plati- 
num are reduced to the metallic state by ignition. 

Protochloride of platinum, PtCl. — The protochloride is produced when 
bichloride of platinum, dried and powdered, is exposed for some time to a 
heat of 400° (204° -5C), by which half of the chlorine is expelled ; also, when 
sulphurous acid is passed into a solution of the bichloride until the latter 
ceases to give a precipitate with sal-ammoniac. It is a greenish-grey pow- 
der, insoluble in water, but dissolved by hydrochloric acid. The latter solu- 
tion, mixed with sal-ammoniac or chloride of potassium, deposits a double 
salt in fine red prismatic crystals, containing in the last case, PtCl-f-KCl. 
The corresponding sodium-compound is very soluble and difficult to crystal- 
lize. The protochloride is decomposed by heat into chlorine and metallic 
platinum. 

Bichloride or perchloride of Platinum, PtCl 2 . — This substance is al- 
ways formed when platinum is dissolved in nitro-hydrochloric acid. The 
acid solution yields on evaporation to dryness a red or brown residue, deli- 
quescent, and very soluble both in water and alcohol ; the aqueous solution 
has a pure orange-yellow tint. Bichloride of platinum combines to double 
salts with a great variety of metallic chlorides ; the most important of these 
compounds are those containing the metals of the alkalis and ammonium. 
Bichloride of platinum and chloride of potassium, PtCl 2 , KG, forms a bright yel- 
low crystalline precipitate, being produced whenever solutions of the chlo- 
rides of platinum and of potassium are mixed, or a salt of potassa, mixed 
with a little hydrochloric acid, added to bichloride of platinum. It is feebly 
soluble in water, still less soluble in dilute alcohol, and is decomposed with 
some difficulty by heat. It is readily reduced by hydrogen at a high tem- 
perature, furnishing a mixture of chloride of potassium and platinum-black ; 
the latter substance may thus, indeed, be very easily prepared. The sodium- 
salt, PtG 2 , NaCl-j-GHO, is very soluble, crystallizing in large, transparent, 
yellow-red prisms of great beauty. The ammonio-chloride of platinum, PtG 2 , 
NH 4 C1, is indistinguishable, in physical characters, from the potassium-salt; 

1 9S-94, Prof. Andrews, Chem. Gar., Oct 1852. 



PLATINUM. 809 

it is thrown down as a precipitate of small, transparent, yellow, octahedral 
crystals when sal-ammoniac is mixed with chloride of platinum ; it is but 
feebly soluble in water, still less so in dilute alcohol, and is decomposed by 
heat, yielding spongy platinum, while sal-ammoniac, hydrochloric acid, and 
nitrogen are driven off. Compounds of platinum with iodine, bromine, sul- 
phur, and phosphorus have been formed, but are comparatively unim- 
portant. 

Some very extraordinary compounds have been derived from the proto- 
chloride of platinum. 

"When ammonia in excess is added to a hot solution of the protochloride 
of platinum and ammonium, a green crystalline salt separates after a time, 
which is quite insoluble in water, and is not affected by hydrochloric or sul- 
phuric acids, ammonia, or even a boiling-hot solution of potassa. This sub- 
stance is known as the green salt of Magnus, and contains the elements of 
protochloride of platinum and ammonia, or PtCl-f-NH 3 . 

When the above compound is heated with concentrated nitric acid, it be- 
comes converted into a white, granular, crystalline powder, which on addition 
of water dissolves, leaving a residue of metallic platinum. The solution 
yields on standing small, brilliant, colourless prisms of a substance very so- 
luble in water, containing the elements of protochloride of platinum, ammo- 
nia, nitric acid, and an additional equivalent of oxygen : — 

PtCl,N 2 H 6 + N0 5 . 

The platinum and chlorine in this curious body are insensible to ordinary 
reagents, and ammonia is evolved from it only on boiling with caustic alkali ; 
the presence of nitric acid can be detected immediately by gently heating a 
small portion with copper-filings and oil of vitriol. Prom this substance a 
series of salt-like bodies can be obtained, some of which have been carefully 
studied by M. Gros. Thus, when treated with hydrochloric acid, the nitric 
acid is wholly displaced, and a compound formed which crystallizes in small, 
transparent, yellowish octahedrons, sparingly soluble in boiling water, con- 
taining PtCl,N 2 H 6 CL With sulphuric acid it gives a substance which crys- 
tallizes in small, sparingly soluble, colourless needles, containing PtCl, 
N 2 H 6 0-f-!80 3 . The oxalic acid compound is white and insoluble ; it contains 
PtCl,N 2 H 6 04-C 2 3 . Crystallizabie compounds containing phosphoric, tar- 
taric, citric, malic, formic, and even carbonic acids, were obtained by similar 
means. These substances have very much the characters of salts of a com- 
pound base or quasi-metal containing PtCl,N 2 H 6 , and which yet remains un- 
known in a separate state. M. Raewsky has repeated and extended the 
observations of M. Gros. 

MM. Reiset and Peyrone have also described two other basic bodies con- 
taining platinum in the same remarkable condition : these differ from the 
preceding in being free from chlorine. 

Protochloride of platinum put into ammonia becomes rapidly converted 
into a green powder, which, by boiling, slowly dissolves ; the solution, on 
evaporation and cooling, furnishes beautiful yellowish crystals of the chlorine- 
compound of one of these bases, compounded of platinum and the elements 
of ammonia. The crystals contained PtN 2 H 6 Cl-j-HO. The equivalent of 
water is easily expelled by heat, and regained by absorption from the air. 
The green salt of Magnus, boiled with ammonia, yields the same product. 

A solution of this substance, mixed with nitrate of silver, gives chloride 
of silver and the nitrate of the new base, which crystallizes on evaporation 
in fine, white, transparent needles, containing PtN 2 H 6 0-f-N0 5 . The sulphide, 
iodide, and bromide are also crystallizabie. Two carbonates exist. By adding 
baryta-water to a solution of the sulphate, or by treating the chloride with 
protoxide of silver, and evaporating the filtered liquid in vacuo, a white, 



310 PLATINUM. 

crystalline, deliquescent mass is obtained, which is the hydrate of the base, 
PtN 2 H 6 0-}-HO. It is almost comparable in point of alkalinity with potassa 
itself, absorbing carbonic acid with energy, and decomposing ammoniacal 
salts. When this hydrate is heated to 280° (110°C), it abandons water and 
ammonia, and leaves a greyish, porous, insoluble mass containing PtNH 3 ,0. 
This is probably an isomeric modification of the second base, whose salts are 
mentioned below. 

When a solution of the iodide, PtN 2 H 6 I, is long boiled, it deposits a spar- 
ingly soluble yellow powder, the composition of which is expressed by the 
formula PtNH 3 I : this is the iodine-compound of a second basic substance, 
PtNH 3 ; and from it by double decomposition a series of analogous salts can 
be obtained. When the iodine-compound is treated with protoxide of silver, 
the base itself is obtained in the form of a powerfully alkaline solution. The 
green salt of Magnus has the same composition as the chloride of this new 
base, which is yellow and soluble in boiling water, and may be converted into 
it. The salts of the first base are generally convertible into those of the 
second by heat, and the converse change may also be often effected by ebul- 
lition with ammonia. 

The subject of the platinum-bases appears to be by no means exhausted. 
Only quite recently another remarkable basic compound containing ammonia 
and platinum has been discovered by M. Gerhardt. The chloride of Reiset's 
second base, the compound PtNH 3 Cl, when treated with chlorine, absorbs 
this element, and becomes converted into a lemon-yellow powder, consisting 
of small octahedrons, and having the composition PtNH 3 Cl 2 . Boiled with 
nitrate of silver, this substance yields chloride of silver and, according to the 
quantity of nitric acid present, a salt, PtNH 3 2 ,2N0 5 , or PtNH 3 2 ,N0 5 -f- 
3HO. On adding ammonia to the latter nitrate, a crystalline precipitate 
takes place, which consists of PtNH 3 2 -|-2HO. This substance, which is 
slightly soluble in water, may be viewed as the hydrated base existing in the 
bichloride and in the nitrates previously described. 



The bichloride, or a solution of binoxide of platinum, can be at once re- 
cognized by the yellow precipitate with sal-ammoniac, decomposable by heat, 
•Vrith production of spongy metal. 



Bichloride of platinum and the sodio-chloride of platinum are employed 
in analytical investigations to detect the presence of potassa, and separate it 
from soda. For the latter purpose, the alkaline salts are converted into 
chlorides, and in this condition mixed with four times their weight of sodio- 
chloride of platinum in crystals, the whole being dissolved in a little water. 
When the formation of the yellow salt appears complete, alcohol is added, 
and the precipitate collected on a weighed filter, washed with weak spirit, 
carefully dried, and weighed. The chloride of potassium is then easily reck- 
oned from the weight of the double salt, and this, subtracted from the weight 
of the mixed chlorides employed, gives that of the chloride of sodium by 
difference; 100 parts of potasso-chloride of platinum correspond to 35 0*6 
parts of chloride of potassium. 

Capsules and crucibles of platinum are of great value to the chemist; the 
latter are constantly used in mineral analysis for fusing siliceous matter with 
alkaline carbonates. They suffer no injury in this operation, although the 
caustic alkali roughens and corrodes the metal. The experimenter must be 
particularly careful to avoid introducing any oxide of any easily fusible 
metal, as that of lead or tin, into a platinum crucible. If reduction should 
by any means occui, these metals will at once alloy themselves with the pla- 



PALLADIUM. oil 

tinum, and the vessel will be destroyed. A platinum crucible must never be 
put naked into the fire, but be always placed within a covered earthen 
crucible. 

PALLADIUM. 

The solution of crude platinum, from which the greater part of that metal 
has been precipitated by sal-ammoniac, is neutralized by carbonate of soda, 
and mixed with a solution of cyanide of mercury ; cyanide of palladium 
separates as a whitish insoluble substance, which, on being washed, dried, 
and heated to redness, yields metallic palladium in a spongy state. The pal- 
ladium is then welded into a mass, in the same manner as platinum. 

Palladium closely corresponds with platinum in colour, appearance, and 
difficult fusibility ; it is also very malleable and ductile. In density it differs 
very much from that metal, being only 11-8. Palladium is more oxidable 
than platinum. When heated to redness in the air, especially in the state 
of sponge, it acquires a blue or purple superficial film of oxide, which is 
again reduced at a white heat. This metal is slowly attacked by nitric acid ; 
its best solvent is aqua regia. There are two compounds of palladium and 
oxygen. 

The equivalent of palladium is 53-3 ; its symbol is Pd. 

Protoxide of palladium, PdO. — This is obtained by evaporating to dry- 
ness, and cautiously heating, the solution of palladium in nitric acid. It is 
black, and but little soluble in acids. The hydrate falls as a dark brown 
precipitate when carbonate of soda is added to the above solution. It is 
decomposed by a strong heat. 

Binoxide or palladium, Pd0 2 . — The pure binoxide is very difficult to 
obtain. When solution of caustic potassa is poured, little by little, with 
constant stirring, upon the double chloride of palladium and potassium in a 
dry state, the latter is converted into a yellowish-brown substance, which is 
the binoxide, in combination with water and a little alkali. It is but feebly 
soluble in acids. 

Protochloride of palladium, PdCl. — The solution of the metal in aqua 
regia yields this substance when evaporated to drynesss. It is a dark brown 
mass, soluble in water when the heat has not been too great, and forms 
double salts with many metallic chlorides. The potassio- and ammonio- 
chlorides of palladium are much more soluble than those of platinum ; they 
have a brownish-yellow tint. 

Bichloride of palladium only exists in solution, and in combination witli 
the alkaline chlorides. It is formed when the protochloride of palladium is 
digested in aqua regia. The solution has an intense brown colour, and is 
decomposed by evaporation. Mixed with chloride of potassium or sal-ammo- 
niac, it gives rise to a red crystalline precipitate of double salt which is but 
little soluble in water. 

A sulphide of palladium, PdS, is formed by fusing the metal with sulphur, 
or by precipitating a solution of protochloride by sulphuretted hydrogen. 



A palladium-salt is well marked by the pale yellowish-white precipitate 
with solution of cyanide of mercury, convertible by heat into the spongy 
metal. This precipitate is a double salt, having the formula PdCy,HgCy, HO. 



Palladium is readily alloyed with other metals, as copper : one of these 
compounds, namely, the alloy with silver, has been applied to useful pur- 
poses. A native alloy of gold with palladium is found in the Brazils, and 
imported into England. 



12 RHODIUM — IRIDIUM, 



RHODIUM. 

The solution from which platinum and palladium have been separated in 
the manner described is mixed with hydrochloric acid, and evaporated to 
dryness. The residue is treated with alcohol of specific gravity 0-837, 
which dissolves everything except the double chloride of rhodium and sodium. 
This is well washed with spirit, dried, heated to whiteness, and then boiled 
with water ; chloride of sodium is dissolved out, and metallic rhodium re- 
mains. Thus obtained, rhodium is a white, coherent, spongy mass, which 
is more infusible and less capable of being welded than platinum. Its spe- 
cific gravity varies from 10-6 to 11. 

Rhodium is very brittle : reduced to powder and heated in the air, it be- 
comes oxidized, and the same alteration happens to a greater extent when it 
is fused with nitrate or bisulphate of potassa. None of the acids, singly or 
conjoined, dissolve this metal, unless it be in the state of alloy, as with pla- 
tinum, in which it is attacked by aqua regia. 

The equivalent of rhodium is 52-2 ; its symbol is It. 

Protoxide of rhodium, KO, is obtained by roasting finely divided me- 
tallic rhodium. It is but little known. 

Sesquioxide of rhodium, E 2 3 . — Finely-powdered metallic rhodium is 
heated in a silver crucible with a mixture of hydrate of potassa and nitre ; 
the fused mass boiled with water leaves a dark brown, insoluble substance, 
consisting of sesquioxide of rhodium in union with potassa. This is digested 
with hydrochloric acid, which removes the potassa and leaves a greenish- 
grey hydrate of the sesquioxide of rhodium, insoluble in acids. A soluble 
modification of the same substance, retaining, however, a portion of alkali, 
may be had by adding an excess of carbonate of potassa to the double chlo- 
ride of rhodium and potassium, and evaporating. 

Sesquichloride of rhodium, Ii 2 Cl 3 . — The pure sesquichloride is prepared 
by adding hydrofluosilicic acid to the double chloride of rhodium and potas- 
sium, evaporating the filtered solution to dryness, and dissolving the residue 
in water. It forms a brownish-red deliquescent mass, soluble in water, with 
a fine red colour. It is decomposed by heat into chlorine and metallic rho- 
dium. The chloride of rhodium and potassium, R 2 C1 3 -f-2KCl-}-2HO, is pre- 
pared by heating in a stream of chlorine a mixture of equal parts finely 
powdered rhodium and chloride of potassium. This salt has a fine red 
colour, is soluble in water, and crystallizes in four-sided prisms. Chloride of 
- rhodium and sodium is also a very beautiful red salt, obtained by a similar 
process; it contains R„Cl 3 -j-3NaCl-|-18HO. The chloride of rhodium and 
ammonium resembles the potassium-compound. 

Sulphate of rhodium, R 2 3 ,3S0 3 . — The sulphide of rhodium, obtained 
by precipitating one of the salts by a soluble sulphide, is oxidized by strong 
nitric acid. The product is a brown powder, nearly insoluble in nitric acid, 
but dissolved by water ; it cannot be made to crystallize. Sulphate of rho- 
dium and potassium, is produced when metallic rhodium is strongly heated 
with bisulphate of potassa. It is a yellow salt, slowly soluble in cold water. 



An alloy of steel with a small quantity of rhodium is said to possess ex- 
tremely valuable properties. 

iridium. 

When crude platinum is dissolved in aqua regia, a small quantity of a grey 
scaly metallic substance usually remains behind, having altogether resisted 
the action of the acid ; this is a native alloy of iridium and osmium. It is 
reduced to powder, mixed with an equal Aveight of dry chloride of sodium, 
und heated to redness in a glass tube, through which a stream of moist chlo- 



IRIDIUM. 313 

rine gas is transmitted. The farther extremity of the tube is connected with 
a receiver containing solution of ammonia. The gas, under these circum- 
stances, is rapidly absorbed, chloride of iridium and chloride of osmium be- 
ing produced : the former remains in combination with the chloride of so- 
dium ; the latter, being a volatile substance, is carried forward into the 
receiver, where it is decomposed by the water into osmic and hydrochloric 
acids, which combine with the alkali. The contents of the tube when cold 
are treated with water, by which the double chloride of iridium and sodium 
is dissolved out ; this is mixed with an excess of carbonate of soda, and 
evaporated to dryness. The residue is ignited in a crucible, boiled with 
water, and dried ; it then consists of a mixture of sesquioxide of iron, and 
a combination of oxide of iridium with soda; it is reduced by hydrogen at 
a high temperature, and treated successively with water and strong hydro- 
chloric acid, by which the alkali and the iron are removed, while metallic 
iridium is left in a divided state. By strong pressure' and exposure to a 
white heat, a certain degree of compactness may be communicated to the 
metal. 

Iridium is a white brittle metal, fusible with great difficulty before the 
oxy-hydrogen blowpipe. 1 It is not attacked by any acid, but is oxidized by 
fusion with nitre, and by ignition to redness in the air. 

The equivalent of iridium is 99. Its symbol is Ir. 

Oxides of iridium. — Four of these compounds are described. Protoxide 
of iridium, IrO, is prepared by adding caustic alkali to the protochloride, 
and digesting the precipitate in an acid. It is a heavy black powder, inso- 
luble in acids. It may be had in the state of hydrate by precipitating the 
protochloride of iridium and sodium by caustic potassa. The hydrate is so- 
luble in acids with dirty green colour. Sesquioxide, Ir 2 O g , is produced when 
iridium is heated in the air, or with nitre ; it is best prepared by fusing in 
a silver crucible a mixture of carbonate of potassa and the terchloride of 
iridium and potassium, and boiling the product with water. This oxide is 
bluish-black, and is quite insoluble in acids. It is reduced by combustible 
substances with explosion. Binoxide of iridium, Ir0 2 , is unknown in a sepa- 
rate state ; it is supposed to exist in the sulphate, produced when the sul- 
phide is oxidized by nitric acid. A solution of sulphate heated with excess 
cf .alkali evolves oxygen gas, and deposits sesquioxide of iridium. Teroxide 
cf iridium, Ir0 3 , is produced when carbonate of potassa is gently heated with 
the terchloride of iridium ; it forms a greyish-yellow hydrate, which con- 
tains alkali. 

ChloFvIDEs of iridium. — Protochloride, IrCl, is formed when the metal is" 
brought in contact with chlorine at a dull red-heat; it is a dark olive-green 
insoluble powder. It is dissolved by hydrochloric acid, and forms double 
salts with the alkaline chlorides, which have a green colour. The sesquiehlo- 
ride, Ir 2 Cl 3 , is prepared by strongly heating iridium with nitre, adding water, 
and enough nitric acid to saturate the alkali, warming the mixture, and then 
dissolving the precipitated hydrate of the sesquioxide in hydrochloric acid. 
It forms a dark yellowish-brown solution. This substance combines with 
metallic chlorides. Bichloride of iridium is obtained in solution by adding 
hydrofluosilicic acid to the bichloride of iridium and potassium, formed 
when chlorine is passed over a heated mixture of iridium and chloride, 
of potassium. It forms with metallic chlorides a number of double salts, 
which resemble the platinum-compounds of the same order. Terchloride cf 
iridium, IrCl 3 , is unknown in a separate state. Terchloride of iridium ana 
potassium is obtained by heating iridium with nitre, and then dissolving the 

1 It is the heaviest substance known, its specific gravity, according to Professor Hare belnir 
21-S. Proceedings of the Anier. Phil. Soc. 3Iay and June, 1842. — K. B 

27 



314 RUTHENIUM — OSMIUM. 

•whole til aqua regia, and evaporating to dryness. The excess of chloride of 
potassium may be extracted by a small quantity of water. The crystallized 
salt has a beautiful red colour. The variety of tints exhibited by the diffe- 
rent soluble compounds of iridium is very remarkable, and suggested the 
name of the metal, from the word iris. 

Platinum, palladium, and iridium combine with carbon when heated in the 
flame of a spirit-lamp ; they acquire a covering of soot, which, when burned, 
leaves a kind of skeleton of spongy metal. 

RUTHENIUM. 

M. Claus has described under this name a new metal contained in the 
residue from crude platinum, insoluble in aqua regia. It closely resembles 
iridium in its general characters, but yet possesses distinctive features of 
its own. It was obtained in the form of small angular masses, with perfect 
metallic lustre, very brittle and infusible. Its specific gravity is 8-6. It 
resists the action of acids, but oxidizes readily when heated in the air. 

The equivalent of ruthenium is 52-2, and its symbol Ru. 

Oxides of ruthenium. — Protoxide of ruthenium, RuO, is a greyish-black 
metallic-looking powder, obtained by heating bichloride of ruthenium with 
excess of carbonate of soda in a stream of carbonic acid gas, and then wash- 
ing away the soluble saline matter. It is insoluble in acids. The sesquioxide, 
Ru 2 3 . in the anhydrous condition is a bluish-black powder formed by heating 
the metal in the air. It is also precipitated by alkalis from the sesquichlo- 
ride as a blackish-brown hydrate, soluble in acids with orange-yellow colour. 
The binoxide, Ru0 2 , is a deep blue powder, procured by roasting the bisul- 
phide. A hydrate of this oxide is known in an impure condition. An acid 
of ruthenium is also supposed to exist. 

Sesquichloride of ruthenium, Ru 2 Cl 3 , is an orange-yellow soluble salt of 
astringent taste ; when the solution is heated, it becomes green and finally 
blue, by reduction, in all probability, to protochloride. Sesquichloride of 
ruthenium forms double salts with the chlorides of potassium and ammonium. 



The solution of osmic acid in ammonia, already mentioned, is gently heated 
for some time in a loosely-stopped vessel ; its oi'iginal yellow colour becomes 
darker, and at length a brown precipitate falls, which is a combination of 
sesquioxide of osmium with ammonia: it results from the reduction of the 
osmic acid by the hydrogen of the volatile alkali. A little of the precipitate 
is held in solution by the sal-ammoniac, but may be recovered by heating 
the clear liquid with caustic potassa. The brown substance is dissolved in 
hydrochloric acid, a little chloride of ammonium added, and the whole evapo- 
rated to dryness. The residue is strongly heated in a small porcelain retort; 
the oxygen of the oxide combines with hydrogen from the ammonia, vapour 
of water, hydrochloric acid, and sal-ammoniac are expelled, and osmium left 
behind, as a greyish porous mass, having the metallic lustre. 

In the most compact state in which this metal can be obtained, it has a 

luish-white colour, and, although somewhat flexible in thin plates, is yet 

asily reduced to powder. Its specific gravity is 10 ; it is neither fusible 

nor volatile. It burns when heated to redness, yielding osmic acid, which 

volatilizes. Osmate of potassa is produced when the metal is fused with 

nitre. When in a finely divided state, it is oxidized by strong nitric acid. 

The equivalent of osmium is 99-6 ; its symbol is Os. 

Oxides of osmium. — Five compounds of osmium with oxygen are known. 
Protoxide, OsO, is obtained, in combination with a little alkali, vhen caustic 
potassa is added to a solution of protochloride of osmium and potassium. It 
is a dark green powder, slowly soluble in acids. Sesquioxide, Os 2 3 , baa 



OSMIUM. 315 

already been noticed ; it is generated by the deoxidalion of osmate of am- 
monia ; it is black, and but little soluble in acids. It always contains 
ammonia, and explodes feebly when heated. Binoxide of osmium, Os0 2 , is pre- 
pared by strongly heating in a retort a mixture of carbonate of soda and the 
bichloride of osmium and potassium, and treating the residue with water, and 
afterwards with hydrochloric acid. The binoxide is a black powder, insoluble 
in acids, and burning to osmic acid when heated in the air. Osmious acid 
Os0 3 is known only in combination. On adding alcohol to a solution of 
osmate of potassa, the alcohol is oxidized at the expense of the osmic acid, 
and a rose-red crystalline powder of osmite of potassa is produced. On at- 
tempting to separate the acid, it is decomposed into the binoxide and osmic 
acid. Osmic acid, 0s0 4 , is by far the most important and interesting of the 
oxides of this metal. It is prepared by heating osmium in a current of pure 
oxygen gas ; it condenses in the cool part of the tube in which the experi- 
ment is made in colourless transparent crystals. Osmie acid melts and even 
boils below 212° (100°C) ; its vapour has a peculiar offensive odour, and is 
exceedingly irritating and dangerous. Water slowly dissolves this substance. 
It has acid properties, and combines with bases. Nearly all the metals pre- 
cipitate osmium from a solution of osmic acid. By the action of ammonia 
on osmic acid, a new acid has been formed, containing osmium, nitrogen, 
and oxygen. It has been called osman-osmic acid or osmamic acid. Some 
doubts are hanging over the formula of this substance. It produces salts 
with many bases. 

Chlorides of osmium. — ProtocMoride, OsCl, is a dark green crystalline 
substance, formed by gently heating osmium in chlorine gas. It is soluble 
in a small quantity of water, with green colour, but decomposed by a large 
quantity into osmic and hydrochloric acids and metallic osmium. It forms 
double salts with the metallic chlorides. The sesquichloride, Os 2 Cl 3 , has not 
been isolated ; it exists in the solution obtained by dissolving the sesquioxide 
iu hydrochloric acid. Bichloride, OsCl 2 , in combination with chloride of 
potassium, is produced when a mixture of equal parts metallic osmium and 
the last-named salt is strongly heated in chlorine gas. It forms fine red oc- 
tahedral crystals, containing OsCl 2 -f-KCl. 

Osmium combines also with sulphur and with phosphorus. 



PAET III. 

ORGANIC CHEMISTRY. 



INTRODUCTION. 



Organic substances, whether directly derived from the vegetable or ani- 
mal kingdom, or produced by the subsequent modification of bodies which 
thus originate, are remarkable as a class for a degree of complexity of con- 
stitution far exceeding that observed in any of the compounds yet described. 
And yet the number of elements -which enter into the composition of these 
substances is extremely limited ; very few, comparatively speaking, contain 
more than four, viz., carbon, hydrogen, oxygen, and nitrogen; sulphur and 
phosphorus are occasionally associated with these in certain mineral pro- 
ducts ; and compounds containing chlorine, bromine, iodine, arsenic, anti- 
mony, zinc, &c, have been formed by artificial means. This paucity of 
elementary bodies is compensated by the very peculiar and extraordinary 
properties of the four first-mentioned, which possess capabilities of combi- 
nation to which the remaining elements are strangers. There appears to be 
absolutely no limit to the number of definite, and often crystallizable, sub- 
stances which can be thus generated, each marked by a perfect individuality 
of its own. 

The mode of association of the elements of organic substances is in gene- 
ral altogether different from that so obvious in the other division of the 
science. The latter is invariably characterized by what may be termed a 
binary plan of combination, union taking place between pairs of elements, 
and the compounds so pi-oduced again uniting themselves to other compound 
bodies in the same manner. Thus, copper and oxygen combine to oxide of 
copper, potassium and oxygen to potassa, sulphur and oxygen to sulphuric 
acid ; sulphuric acid, in its turn, combines both with oxide of copper and oxide 
of potassium, generating a pair of salts, which are again capable of uniting 
to form the double compound, CuO,SO s -f-KO,S0 3 . 

The most complicated products of inorganic chemistry may be thus shown 
to be built up by this repeated pairing on the part of their constituents. 
With organic bodies, however, the case is strikingly different ; no such ar- 
rangement can here be traced. In sugar, C l2 H n O n , or morphine, C 34 H 19 N0 6 , 
or the radical of bitter almond oil, C J4 H 5 2 , and a multitude of similar cases, 
the elements concerned are, as it were, bound up together into a single 
wdiole, which can enter into combination with other substances, and be thence 
disengaged with properties unaltered. 

A curious consequence of this peculiarity is to be found in the compara- 
tively instable character of organic compounds, and their general proneness 
to decomposition and change, when the balance of opposing forces, to which 
they owe their existence, becomes deranged by some external cause. 

If a complex inorganic substance be attentively considered, it will usually 
be found that the elements are combined in such a manner as to satisfy the 
most powerful affinities, and to give rise to a state of vei*y considerable per- 
manence and durability But in the case of an organic substance containing 

(316) 



INTRODUCTION TO ORGANIC CHEMISTRY. 317 

three or four elements associated in the way described, this is very far from 
being true : the carbon and oxygen strongly tend to unite to form carbonic 
acid ; the hydrogen and oxygen attract each other in a powerful manner, 
and the nitrogen, if that body be present, also contributes its share to these 
internal sources of weakness by its disposition to generate ammonia. While 
the opposing forces remain exactly balanced, the integrity of the compound 
is preserved ; but the moment one of them, from some accidental cause, 
acquires preponderance over the rest, equilibrium is destroyed and the 
organic principle breaks up into two or more new bodies of simpler and more 
permanent constitution. The agency of heat produces this effect by 
exalting the attraction of oxygen for hydrogen and carbon ; hence the almost 
universal destructibility of organic substances by a high temperature. Mere 
molecular disturbance of any kind may cause destruction when the insta- 
bility is very great. 

As a general rule, it may be assumed that those "bodies which are most 
complex from the number of elements, and the want of simplicity in their 
equivalent relations, are by constitution weakest, and least capable of resist- 
ing the action of disturbing forces ; and that this susceptibility of change 
diminishes with increased simplicity of structure, until it reaches its minimum 
in those bodies which, like the carbides of hydrogen, like cyanogen, and 
oxalic acid, connect, by imperceptible gradations, the organic and the mineral 
departments of chemical science. 

The definite organic principles of the vegetable and animal kingdoms form 
but a very small proportion of the immense mass of compounds included 
within the domain of organic chemistry : by far the greater number of these 
are produced by modifying by suitable means the bodies furnished by the 
plant or the animal, and which have themselves been formed from the 
elements of the air by processes for the most part unknown, carried on under 
the control of vitality. Unlike these latter, the artificial modifications 
referred to, by oxidation, by the action of other powerful reagents, by the 
influence of heat, and by numerous other sources of disturbance, are, for 
the most part, changes of descent in order of complexity, new products being 
thus generated more simple in constitution and more stable in character than 
the bodies from which they were derived. These, in turn, by repetition of 
such treatment under perhaps varied circumstances, may be broken up into 
other and still simpler organic combinations ; until at length the biuary 
compounds of inorganic chemistry, or bodies so allied to them that they may 
be placed indifferently in either group, are by such means reached. 

Organic Substitution-products : Laio of Substitution. — The study of the action 
of chlorine, bromine, iodine, and nitric acid upon various organic substances 
has led to the discovery of a very remarkable law regulating the formation 
of chlorinetted and other analogous compounds, which, without being of 
necessity absolute in every case, is yet of sufficient generality and import- 
ance to require careful consideration. This peculiar mode of action consists 
in the replacement of the hydrogen of the organic substance by chlorine, 
bromine, iodine, the elements of hyponitric acid, and more rarely other sub- 
stances of the same class, equivalent for equivalent, without the destruction 
of the primitive type or constitution of the compound so modified. The 
hydrogen thus removed takes of course the form of hydrochloric or hydro- 
bromic acid, &c, or that of water, by combination with another portion of 
the active body. Strange as it may appear, and utterly opposed to the ordi- 
nary views of the functions of powerful salt-radicals, this loss of hydrogen 
and assumption of the new element do actually occur with a great variety 
of substances belonging to different groups with comparatively trifling dis ■ 
turbance of physical and chemical properties ; the power of saturation, the 
density of the vapour, and other pecularities of the original substance remain 
27* 



318 INTRODUCTION TO 

the same, saving the modification they may suffer from the difference of the 
equivalent -weights of hydrogen and the bodies by which it is replaced. 

This change may take place by several successive steps, giving rise to a 
s> n -ies of substitution-compounds, which depart more and more in properties 
from the original substance with each successive increase in the proportion 
of the replacing body. The substitution may even be total, the whole of the 
hydrogen being lost, and its place supplied by a similar number of equiva- 
lents of the new element. And even in these extreme cases, of very common 
occurrence, however, with one class of substances, the resulting compound 
retains generally the stamp of its origin. 

Although numerous examples of these changes will be found described in 
detail in the following pages, it will be well perhaps to mention here two or 
three cases by way of illustration. 

Dutch-liquid, the compound formed by the union of equal measures of 
defiant gas and chlorine, containing C 4 H 4 C1 2 , is affected by chlorine in 
obedience to the law of substitution ; one, two, three, four equivalents of 
hydrogen being successively removed by the prolonged action of the gas 
aided by sunshine, and one, two, three, or four equivalents of chlorine intro- 
duced in place of the hydrogen withdrawn as hydrochloric acid. In the last 
product, the sesquichloride of carbon, C 4 G 6 , the replacement is total; the 
intermediate products are volatile liquids not differing very much in general 
characters from Dutch-liquid itself. A great number of compound ethers 
of the ethyl- and methyl-series are attacked by chlorine and bromine in a 
similar manner; indeed, the majority of the examples of the law in question 
are to be found in the history of this class of bodies. 

Concentrated acetic acid, placed in a vessel of dry chlorine and exposed to 
the sun, gives rise to chloracetic acid, containing C 4 C1 3 3 ,H0, and in which, 
consequently, the whole hydrogen of the real acid is replaced by chlorine. 
Chloracetic acid is a stable substance, of strong acid characters, and forms 
a series of salts, some of which bear no slight resemblance to the normal ace- 
tates. 

Basic substitution-products have been obtained indirectly; chloraniline, 
bromaniline, and iodaniline are the most striking examples. These will be 
found fully described in the sections on organic bases. 

The action of fuming nitric acid upon organic substances very commonly 
indeed gives rise to substitution-products containing the elements of hypo- 
nitric acid, N0 4 , in place of hydrogen. The benzoyl-compounds, and several 
of the essential oils natural and derived from resins, will be found to furnish 
illustrations. 

In formulae representing substitution-compounds retaining some hydrogen, 
the practice is often adopted of placing the substituting body beneath or be- 
sides this residual hydrogen, and uniting them by a bracket on each side. 
Thus, the formulas of the first two products of the action of chlorine on Dutch- 
liquid are thus written : — 



C 4 {^} C l 2 ,andC 4 {^ 



And pyroxlin, or gun-cotton, which is supposed to be a substitution-product 
from lignin, C 24 H 20 O 20 , having 5 equivalents of hydrogen replaced by the ele- 
ments of hyponitric acid, will stand: — 

C 24 { 5N0 4 } °so' or C 24 [H 15 (N0 4 ) 5 ] O 20 . 

Isomeric bodies, or substances different in properties, yet identical in com- 
position, are of constant occurrence in organic chemistry, and stand, indeed, 
among its most striking and peculiar features. Every year brings to light 
fresh examples of compounds so related. In most cases, discordance in prq- 



ORGANIC CHEMISTRY. 8H 

perties is fairly and properly ascribed to difference of constitution, the ele- 
ments being differently arranged. For instance, formic ether and acetate of 
methyl are isomeric, both containing C 6 H 6 4 ; but then the first is supposed 
to consist of formic acid, C 2 H0 3 , combined with ether, C 4 H 5 ; while the 
second is imagined in accordance with the same views, to be made up of ace- 
tic acid, C 4 H 3 3 , and the ether of wood-spirit, C 2 H 3 0. And this method of 
explanation is generally sufficient and satisfactory ; when it can be shown 
that a difference of constitution, or even a difference in the equivalent num- 
bers, exists between two or more bodies identical in ultimate composition, 
the reason of their discordant characters becomes to a certain extent intelli- 
gible. 

Organic bodies may be thus classified : — 

1. Quasi-elementary Substances, and their compounds. — These affect the 
disposition and characters of the true elements, and, like the latter, evince a 
tendency to unite on the one hand with Irvdrogen and the metals, and on the 
other with chlorine, iodine, and oxygen. The former are designated organic 
salt-radicals, and the latter organic salt-basyles. Few of either kind have been 
yet isolated, and it is very possible that very many of them are unable to 
exist in a separate state. Some of these quasi-elements are among the most 
important and interesting substances in organic chemistry. 

2. Organic Salt-bases, not being the oxides of known radicals. — The prin- 
cipal members of this class are the vegeto-alkalis ; they form crystallizable 
compounds with acids, organic and inorganic, and even possess in some cases 
a distinct alkaline reaction to test-paper. 

3. Organic acids, not being compounds of known radicals. — These bodies 
are very numerous and important. Many of them have an intensely sour 
taste, redden vegetable blues, and are almost comparable in chemical energy 
with the acids of mineral origin. 

4. Neutral non-azotized substances, containing oxygen and hydrogen in the 
proportions to form water. — The term neutral, as applied to these compounds, 
is not strictly correct, as they usually manifest feeble acid properties by com- 
bining with metallic oxides. This group comprehends the sugars, the dif- 
ferent modifications of starch, gum, &c. 

5. Neutral azotized substances ; the albuminous principles and their allies, 
the great components of the animal frame. — These are in the highest degree 
complex in constitution, and are destitute of the faculty of crystallization. 

6. Carbides of Hydrogen, their oxides and derivatives. 

7. Fatty bodies. 

8. Compound acids, containing the elements of an organic substance in com- 
bination with those of a mineral or other acid. — These bodies form a largo 
and very interesting class, of which sulphovinic acid may be taken as the 
type or representative. 

9. Colouring principles, and other substances not referable to either of the 
preceding classes. 

The, action of heat on organic substances presents many important and 
interesting points, of which a few of the more prominent may be noticed. 
Bodies of simple constitution and of some permanence, which do not sublime 
unchanged, as many of the organic acids, yield, when exposed to a high, but 
regulated temperature, in a retort, new compounds, perfectly definite and 
often crystallizable, which partake, to a certain extent, of the properties of 
the original substance ; the numerous pyro-acids, of which many examples 
will occur in the succeeding pages, are thus produced. Carbonic acid and 
water are often eliminated under these circumstances. If the heat be sud- 
denly raised to redness, then the regularity of the decomposition vanishes, 
while the products become more uncertain and more numerous ; carbonic 
acid and watery vapor are succeeded by inflammable gases as carbonic oxide 



320 THE ULTIMATE ANALYSIS OF 

and carbonetted hydrogen ; oily matter and tar distil over, and increase in 
quantity until the close of the operation, when the retort is found to contain, 
in most cases, a residue of charcoal. Such is destructive distillation. 

If the organic substance contain nitrogen, and be not of a kind capable 
of taking a new and permanent form at a moderate degree of heat, then 
that nitrogen is in most instances partly disengaged in the shape of ammo- 
nia, or substances analogous to it, partly left in combination with the carbo- 
naceous matter in the distillatory vessel. The products of dry distillation 
thus become still more complicated 

A much greater degree of regularity is observed in the effects of heat on 
fixed organic matters, when these are previously mixed with an excess of 
strong alkaline base, as potassa or lime. In such cases an acid, the nature 
of which is chiefly dependent upon the temperature applied, is produced, and 
remains in union with the base, the residual element or elements escaping 
in some volatile form. Thus, benzoic acid distilled with hydrate of lime, at 
a dull red-heat, yields carbonate of lime and a bicarbide of hydrogen, ben- 
zole ; woody fibre and caustic potassa, heated to a very moderate tempera- 
ture, yield ulmic acid and free hydrogen ; with a higher degree of heat, 
oxalic acid appears in the place of the ulmic ; and, at the temperature of 
ignition, carbonic acid, hydrogen being the other product. 

The spontaneous changes denominated decay and pulref action, to which 
many more of the complicated organic, and, more particularly, azotized prin- 
ciples are subject, have lately attracted much attention. By the expression 
decay, 1 Liebig and his school understand a decomposition of moist organic 
matter, freely exposed to the air, by the oxygen of which it is gradually 
burned and destroyed, without sensible elevation of temperature ; the term 
putrefactio7i, on the other hand, is limited to changes occurring in and be- 
neath the surface of water, the effect being a mere transposition of ele- 
ments, or metamorphosis of the organic body. The conversion of sugar into 
alcohol and carbonic acid furnishes, perhaps, the simplest case of the kind. 
It is proper to remark, however, that contact of oxygen is indispensable, in 
the first instance, to the change, which, when once begun, proceeds, without 
the aid of any other substance external to the decomposing body, unless it 
be water or its elements. Every case of putrefaction thus begins with de- 
cay ; and if the decay or its cause, namely, the absorption of oxygen, be 
prevented, no putrefaction occurs. The most putrescible substances, as an- 
imal flesh intended for food, milk, and highly azotized vegetables, are pre 
served indefinitely, by enclosure in metallic cases, from which the air has 
been completely removed and excluded. 

Some of the curious phenomena of communicated chemical activity, where 
a decomposing substance seems to involve others in destructive change, 
which, without such influence, would have remained in a permanent and 
quiescent state, will be found noticed in their proper places, as under the 
head of Vinous Fermentation. These actions are yet very obscure, and re- 
quire to be discussed with great caution. 



THE ULTIMATE ANALYSIS OF OEGANIC BODIES. 

As organic substances cannot be produced at will from their elements, the 
analytical method of research is alone applicable to the investigation of their 
exact chemical composition ; hence the ultimate analysis of these substances 
becomes a matter of great practical importance. The operation is always 
executed by causing complete combustion of a known weight of the body to 

1 Or ei-emacausis, that is, slow burning. 



ORGANIC BODIES 



be examined, in such a manner that the carbonic acid and water produced 
shall be collected, and their quantity determined ; the carbon and hydrogen 
they respectively contain may from these data be easily calculated. When 
nitrogen, sulphur, phosphorus, chlorine, &c, are present, special and sepa- 
rate means are resorted to for their estimation. 

The method to be described for the determination of the carbon and hy- 
drogen owes its convenience and efficiency to the improvements of Professor 
Liebig ; it has superseded all other processes, and is now invariably employed 
in inquiries of the kind. With proper care, the results obtained are wonder- 
fully correct; and equal, if not surpass in precision, those of the best 
mineral analyses. The principle upon which the whole depends is the fol- 
lowing : — When an organic substance is heated with the oxides of copper, 
lead, and several other metals, it undergoes complete combustion at the ex- 
pense of the oxygen of the oxide, the metal being at the same time reduced, 
either completely or to a lower state of oxidation. 'This effect takes place 
with greatest ease and certainty with the black oxide of copper, which, al- 
though unchanged by heat alone, gives up oxygen to combustible matter 
with extreme facility. When nothing but carbon and hydrogen, or those bo- 
dies together with oxygen, are present, one experiment suffices ; the carbon 
and hydrogen are determined directly, and the oxygen by difference. 

It is of course indispensable that the substance to be analyzed should 
possess the physical characters of purity, otherwise the inquiry cannot lead 
to any good result; if in the solid state, it must also be freed with the most 
scrupulous care from the moisture which many substances retain with great 
obstinacy. If it will bear the application of moderate heat, this desiccation 
is very easily accomplished by a water or steam-bath ; in other cases, expo- 
sure at common temperatures to the absorbent powers of a large surface of 
oil of vitriol in the vacuum of an air-pump must be substituted. 

The operation of weighing the dried powder is conducted in a narrow open 
tube (fig. 153), about 2J or 3 inches long; the tube 
and substance are weighed together, and, when the 
latter has been removed, the tube with any little 
adherent matter is re-weighed. This weight, sub- 
tracted from the former, gives the weight of the sub- 
stance employed in the experiment. As only 5 or 6 
grains are used, the weighings should not evolve a 
greater error than -^th part of a grain. 

The protoxide of copper is best made from the 
nitrate by complete ignition in an earthen crucible : 
it is reduced to powder, and re-heated just before 
use, to expel hygroscopic moisture, which it absorbs, 
even while warm, with avidity. The combustion is 
performed in a tube of hard white Bohemian glass, 

having a diameter of 0-4 or 0-5 inch, and in length varying from 14 to 18 
inches ; this kind of glass bears a moderate red-heat without becoming soft 
enough to lose its shape. One end of the tube is drawn out to a point, as 
shown in fig. 154, and closed; the other is simply heated to fuse and soften 
the sharp edges of the glass. The tube is now two-thirds filled with the ye' 



Fig. 153. 




Fig. 154. 
Oxide copper. Mixture. 



Oxide copper. 



822 



THE ULTIMATE ANALYSIS OP 



•warm protoxide of copper, nearly the whole of which is transferred to a 
small porcelain or Wedgwood mortar, and very intimately mixed with the 
organic substance. The mixture is next transferred to the tube, and the 
mortar rinsed with a little fresh and hot oxide, which is added to the rest; 
the tube is, lastly, filled to within an inch of the open end with oxide from 
the crucible. A few gentle taps on the table suffice to shake together the 
contents, so as to leave a free passage for the evolved gases from end to end. 
The arrangement of the mixture and oxide in the tube is represented in the 
sketch. 

The tube is then ready to be placed in the furnace or chauffer : this latter 
is constructed of thin sheet-iron, and is furnished with a series of supports 
of equal height, which serve to prevent flexure in the combustion-tube when 
softened by heat. Fig. 155. The chauffer is placed upon flat bricks or a 

Fig. 155. 




piece of stone, so that but little air can enter the grating, unless the whole 
be purposely raised. A slight inclination is also given towards the extremity 
occupied by the mouth of the combustion-tube, which passes through a holo 
provided for the purpose. 

To collect the water produced in the experiment, a small light tube of the 
form represented in fig. 156, filled with fragments of spongy chloride of cal- 
cium, is attached by a perforated cork, thoroughly dried, to the open ex- 



Fig. 156. 



Fig. 157. 




tremity of the combustion-tube. The carbonic acid is condensed into a solu- 
tion of caustic potassa, of specific gravity 1-27, which is contained in a small 
glass apparatus on the principle of a Woulfe's bottle, shown in fig. 157. 
The connection between the latter and the chloride of calcium-tube is com- 
pleted by a little tube of caoutchouc, secured with silk cord. The whole is 
shown in fig. 158, as arranged for use. Both the chloride of calcium-tube 
und the potass-apparatus are weighed with the utmost care before the ex- 
periment. 

The tightness of the junctions may be ascertained by slightly rarefying 
the included air by sucking a few bubbles from the interior through the 
liquid, using the dry lips, or better, a little bent tube with a perforated cork : 
U the difference of the level of the liquid in the two limbs of the potass- 



ORGANIC BODIES. 323 

apparatus be preserved for several minutes, the joints are perfect. Red- 
hot charcoal is now placed around the anterior portion of the combustion- 
Fig. 158. 




Drawing of the whole arrangement. 

tube, containing the pure oxide of copper, and when this is red-hot, the fire 
is slowly extended towards the farther extremity by shifting the moveable 
screen g, represented in the drawing. The experiment must be so conducted, 
that an uniform stream of carbonic acid shall enter the potass-apparatus by 
bubbles which may be easily counted: when no nitrogen is present, these 
bubbles are towards the termination of the experiment almost completely 
absorbed by the alkaline liquid, the little residue of air alone escaping. In 
the case of an azotized body, on the contrary, bubbles of nitrogen gas, pass 
through the potassa-solution during the whole process. 

When the tube has become completely heated from end to end, and no 
more gas is disengaged, but, on the other hand, absorption begins to be 
evident, the coals are removed from the farther extremity of the combustion- 
tube, and the point of the latter broken off. A little air is drawn through 
the whole apparatus, by which the remaining carbonic acid and watery 
vapour are secured. The parts are, lastly, detached, and the chloride of 
calcium tube and potass-apparatus re-weighed. The following account of a 
real experiment will serve as an illustration ; the substance examined was 
crystallized sugar. 

Quantity of sugar employed 4-750 grains. 

Potass-apparatus weighed after experiment.... 781-13 
" " before experiment.. 773-82 

Carbonic acid 7-31 

Chloride of calcium-tube after experiment 226-05 

" " before experiment ... 223-30 

Water 2-75 

7-31 gr. carbonic acid=l-994 gr. carbon: and 2-75 gr. water=0-3056 gi 
hydrogen ; or in 100 parts of sugar, 1 

* The theoretical composition of sugar C12H11O11, reckoned to 100 parts gives — 

Carbon 4211 

Hydrogen 6-43 

Oxygen 51-46 

100-00 




824 THE ULTIMATE ANALYSIS OF 

Carbon 41-98 

Hydrogen 6-43 

Oxygen, by difference 51-59 

100-00 

When the organic substances cannot be mixed with the protoxide of copper 
in the manner described, the process must be slightly modified to meet the 
particular case. If, for example, a volatile liquid is to be examined, it is 
enclosed in a little glass bulb with a narrow stem, which is weighed before 
and after the introduction of the liquid, the point being hermetically sealed. 
The combustion-tube must have, in this case, a much greater length ; and, 
as the protoxide of copper cannot be introduced hot, it must be ignited and 
cooled out of contact with the atmosphere, to pre- 
Fig. 159. vent absorption of watery vapour. This is most 

conveniently effected by transferring it, in a heated 
state, to a large platinum crucible, to which a 
close-fitting cover can be adapted. When quite 
cold, the cover is removed, and instantly replaced 
by a dry glass funnel, by the assistance of which 
the oxide may be directly poured into the com- 
bustion-tube, with mere momentary exposure to 
the air. A little oxide is put in, then the bulb, 
with its stem broken at a, fig. 159, a file-scratch 
having been previously made ; and lastly, the tube 
is filled with the cold and dry protoxide of copper. 
It is arranged in the chauffer, the chloride of 
calcium tube and potass-apparatus adjusted, and 
then, some six or eight inches of oxide having been heated to redness, the 
liquid in the bulb is, by the approximation of a hot coal, expelled, and slowly 
converted into vapour, which, in passing over the hot oxide, is completely 
burned. The experiment is then terminated in the usual manner. Fusible 
fatty substances, and volatile concrete bodies, as camphor, require rather 
different management, which need not be here described. 

Protoxide of copper, which has been used, may be easily restored by 
moistening with nitric acid, and ignition to redness; it becomes, in fact, 
rather improved than otherwise, as after frequent employment its density is 
increased, and its troublesome hygroscopic powers diminished. For sub- 
stances which are very difficult of combustion, from the large proportion of 
carbon they contain, and for compounds into which chlorine enters as a con- 
stituent, fused and powdered chromate of lead is very advantageously sub- 
stituted for the protoxide of copper. Chromate of lead freely gives up 
oxygen to combustible matters, and even evolves, when strongly heated, a 
little of that gas, which thus ensures the perfect combustion of the organic 
body. 

Analysis of azotized Substances. — The presence of nitrogen in an organic 
compound is easily ascertained by heating a small portion with solid hydrate 
of potassa in a test-tube ; the nitrogen, if present, is converted into ammo- 
nia, which may be recognized by its odour and alkaline reaction. There are 
several methods of determining the proportion of nitrogen in azotized organic 
substances, the experimenter being guided in his choice of means by the 
nature of the substance and its comparative richness in that element. The 
carbon and hydrogen are first determined in the usual manner, a longer tube 
than usual is employed, and four or five inches of its anterior portion filled 
witn spongy metallic copper, made by reducing the protoxide by hydrogen ; 
this serves to decompose any nitrous acid or bmoxide of nitrogen, which may 



ORGANIC BODIE S. 



825 



ho formed in the act of combustion. During the experiment some idea of 
thb abundance or paucity of the nitrogen may be formed from the number 
of bubbles of incondensible gas which traverse the solution of potassa. 

In the case of compounds abounding in nitrogen, and readily burned by 
protoxide of copper, a method may be employed, which is very easy of execu- 
tion ; this consists in determining the ratio borne by the liberated nitrogen 
to the carbonic acid produced in the combustion. A tube of hard glass, of 
the usual diameter, and about 15 inches long, is sealed at one end ; a little 
of the organic substance, mixed with protoxide of copper, is introduced, and 
allowed to occupy about two inches of the tube ; about as much pure oxide 
is placed over it, and then another portion of a similar mixture ; after which 
the tube is filled up with a second and larger portion of the pure oxide, and 
a quantity of spongy metallic copper. A short bent tube, made moveable 
by a caoutchouc joint, is fitted by a perforated cork, and made to dip into a 
mercurial trough, while the combustion-tube itself. rests in the chauffer. 
(Fig. 160.) 

Fig. 160. 




* Volumes of the two 



Fire is first applied to the anterior part of the tube containing the metal 
and unmixed oxide, and, when this is red-hot, to the extreme end. Com- 
bustion of the first portion of the mixture takes place, the gaseous products 
sweeping before them nearly the whole of the air of the apparatus. j- is- 16 j # 
When no more gas issues, the tube is slowly heated by half an inch 
at a time, in the usual manner, and all the gas very carefully col- 
lected in a graduated jar, until the operation is at an end. The 
volume is then read off, and some strong solution of caustic po- 
tassa thrown up into the jar by a pipette with a curved extremity. 
(Fig. 161.) "When the absorption is complete, the residual volume 
of nitrogen is observed, and compared with that of the mixed 
gases, proper correction being made for difference of level in the 
mercury, and from these data the exact proportion borne by the 
nitrogen to the carbon can be at once determined. 1 

If the proportion of nitrogen be but small, the error from the ni- 
trogen of the residual atmospheric air becomes so great as to de- 
stroy all confidence in the result of the experiment ; and the same 
thing happens when the substance is incompletely burned by pro- 
toxide of copper; other means must then be employed. The 



represents equivalents ; for 
100 cubic inches carbonic acid weigh 47"26 grains. 
100 „ nitrogen „ 30-14 

47-26 : 30-14 = 22 : 14-01 

The last two terms are the equivalent numbers: one equivalent of carbonic wt tcntAina 
one equivalent of carbon. 
28 



326 



THE ULTIMATE ANALYSIS OP 



absolute method of determination, also known by the name of Dumas's me- 
thod, may be had recourse to when the foregoing, or comparative method, 
fails from the first cause mentioned ; it gives excellent results, and is appli- 
cable to all azotized substances. 

A tube of good Bohemian glass, 28 inches long, is securely sealed at one 
end; into this enough dry bicarbonate of soda is put to occupy G inches. A 
little pure protoxide of copper is next introduced, and afterwards the mix- 
ture of oxide and organic substance, the weight of the latter, between 4-5 
and 9 grains, in a dry state, having been correctly determined. The remain- 
der of the tube, amounting to nearly one-half of its length, is then filled up 
with pure protoxide of copper and spongy metal, and a round cork, perfo- 
rated by a piece of narrow tube, is securely adapted to its mouth. This 
tube is connected by means of a caoutchouc joint with a bent delivery tube, 
a, fig. 162, and the combustion-tube arranged in the furnace. A few coals 

Fig. 162. 




b=-=i 



ar e now applied to the farther end of the tube, so as to decompose a portion 
of the bicarbonate of soda, the remainder of the carbonate as well as of the 
other part of the tube being protected from the heat by a screen n. The 
current of carbonic acid thus produced is intended to expel all the air from 
the apparatus. In order to ascertain that this object, on which the success 
of the whole operation depends, is accomplished, the delivery-tube is de- 
pressed under the level of a mercurial trough, and the gas, which is evolved, 
collected in a test-tube filled with concentrated potassa-solution. If the gas 
be perfectly absorbed, or, after the introduction of a considerable quantity, 
only a minute bubble be left, the air maybe considered as expelled. The next 
step is to fill a graduated glass-jar two-thirds with mercury and one-third 
with a strong solution of potassa, and to invert it over the delivery-tube, as 
represented in fig. 162. 

This done, fire is applied to the tube, commencing at the front end, and 
gradually proceeding to the closed extremity, which yet contains some unde- 
composed bicarbonate of soda. This, when the fire at length reaches it, 
yields up carbonic acid, which chases forward the nitrogen lingering in the 
tube. The carbonic acid generated during the combustion is wholly absorbed 
by the potassa in the jar, and nothing is left but the nitrogen. When the 
operation is at an end, the jar, with its contents, is transferred to a vessel 
of water, and the volume of the nitrogen read off. This is properly corrected 
for temperature, pressure, and aqueous vapour, and its weight determined 
by calculation. When the operation has been very successful, and all pre- 
cautions minutely observed, the result still leaves an error in excess, amount- 
ing to 0-3 or 0-5 per cent., due to the residual air of the apparatus, or that 
condensed into the pores of the protoxide of copper. 

A most elegant process for estimating nitrogen in all organic compounds, 
except those containing the nitrogen in the form of nitrous, hyponitric and 



ORGANIC BODIES. 827 

nitric acids, has been put into practice by MM. Will and Varrentrapp. When 
a non-azotized organic substance is heated to redness with a large excess of 
hydrate of potassa or soda, it suffers complete and speedy combustion at the 
expense of the water of the hydrate, the oxygen combining with the carbon 
of the organic matter to carbonic acid, which is retained by the alkali, while 
its hydrogen, together with that of the substance, is disengaged, sometimes 
in union with a little carbon. The same change happens when nitrogen is 
present, but with this addition : the whole of the nitrogen thus abandoned 
combines with a portion of the liberated hydrogen to form ammonia. It is, 
evident, therefore, that if this experiment be made on a weighed quantity 
of matter, and circumstances allow the collection of the whole of the ammonia 
thus produced, the proportion of nitrogen can be easily calculated. 

An intimate mixture is made of 1 part caustic soda, and 2 or 3 parts quick- 
lime, by slaking lime of good quality with the proper proportion of strong 
caustic soda, drying the mixture in an iron vessel, and then heating it to 
strong redness in an earthen crucible. The ignited mass is rubbed to powder 
in a warm mortar, and carefully preserved from the air. The lime is useful 
in many ways : it diminishes the tendency to deliquescence of the alkali, fa- 
cilitates mixture with the organic substance, and prevents fusion and lique- 
faction. A proper quantity of the substance to be analyzed, from 5 to 10 
grains namely, is dried and accurately weighed out ; this is mixed in a warm 
porcelain mortar with enough of the soda-lime to fill two-thirds of an ordi- 
nai-y combustion-tube, the mortar being rinsed with a little more of the 
alkaline mixture, and, lastly, with a small quantity of powdered glass, which 
completely removes everything adherent to its surface; the tube is then filled 
to within an inch of the open end with the lime-mixture, and arranged in 
the chauffer in the usual manner. The ammonia is collected in a little ap- 
paratus of three bulbs (fig. 163) containing moderately strong hydrochloric 

Fis. 163. 




acid, attached by a cork to the combustion-tube. Matters being thus ad- 
justed, fire is applied to the tube commencing with the anterior extremity. 
When ignited throughout its whole length, and when no more gas issues from 
the apparatus, the point of the tube is broken, and a little air drawn through 
the whole. The acid liquid is then emptied into a capsule, the bulbs rinsed 
into the same, first with a little alcohol, and then repeatedly with distilled 
water ; an excess of pure bichloride of platinum is added, and the whole 
evaporated to dryness in a water-bath. The dry mass, when cold, is treated 
with a mixture of alcohol and ether, which dissolves out the superfluous bi- 
chloride of platinum, but leaves untouched the yellow crystalline double 
chloride of platinum and ammonium. The latter is collected upun a small 
weighed filter, washed with the same mixture of alcohol and ether, dried at 
212° (100°C), and weighed ; 100 parts correspond to 6-272 parts of nitrogen ; 
or, the salt with its filter maybe very carefully ignited, and the filter burned 
in a platinum crucible, and the nitrogen reckoned from the weight of the 
spongy metal, 100 parts of that substance corresponding to 14-18 parts of 
nitrogen. The former plan is to be preferred in most cases. 



328 ULTIMATE ANALYSIS OF ORGANIC BODIES. 

Bodies very rich in nitrogen, as urea, must be mixed with about an equa\ 
quantity of pure sugar, to furnish incondensible gas, and thus diminish the 
violence of the absorption which otherwise occurs ; and the same precaution 
must be taken, for a different reason, with those which contain little or no 
hydrogen. 

A modification of this process has been lately suggested by M. Peligot, 
which is very convenient if a large number of nitrogen-determinations are 
to be made. By this plan the ammonia, instead of being received in hydro- 
chloric acid, is conducted into a known volume (from J to 1 cubic inch) of 
a standard solution of sulphuric acid, contained in the ordinary nitrogen- 
bulbs. After the combustion is finished, the acid containing the ammonia is 
poured out into a beaker, coloured with a drop of tincture of litmus, and 
then neutralized with a standard solution of soda in water or of lime in 
sugar-water, the point of neutralization becoming perceptible by the sudden 
appearance of a blue tint. The lime-solution is conveniently poured out 
from the graduated glass-tube, fig. 136, described under the head of alkali- 
metry (page 227). The volume of lime-solution necessary to neutralize the 
same amount of acid, which is used for condensing the ammonia, having 
been ascertained by a preliminary experiment, it is evident that the differ- 
ence of the quantities used in the two experiments gives the ammonia col- 
lected during the combustion in the acid ; the amount of nitrogen may thus 
be calculated. If, for instance, an acid be prepared, containing 20 grains 
of pure hydrated sulphuric acid (S0 3 ,HO) in 1,000 grain-measures — 200 
grain-measures of this acid — the quantity introduced into the bulbs — cor- 
respond to 1-38 grains of ammonia, or 1-14 grains of nitrogen. The alka- 
line solution is so graduated that 1,000 grain-measures will exactly neutra- 
lize the 200 grain-measures of the standard acid. If we now find that the 
acid partly saturated with the ammonia, disengaged during the combustion 
of a nitrogenous substance, requires only 700 grain-measures of the alkaline 

solution, it is evident that — 77^7; — — 60 grain-measures were saturated 

by the ammonia, and the quantity of nitrogen is obtained by the proportion 

1-14 x 60 
200 : 1-14 = 60 : x, wherefrom x = — - — = 0-342 grains of nitrogen. 

Estimation of Sulphur in organic compounds. — When bodies of this class 
containing sulphur are burned with protoxide of copper, a small tube con- 
taining binoxide of lead must be interposed between the chloride of calcium 
tube and the potass-apparatus to retain any sulphurous acid which may be 
formed. It is better, however, to use chromate of lead in such cases. The 
proportion of sulphur is determined by oxidizing a known weight of the sub- 
stance by strong nitric acid, or by fusion in a silver vessel with ten or twelve 
times its weight of pure hydrate of potassa and half as much nitre. The 
sulphur is thus converted into sulphuric acid, the quantity of which can be 
determined by dissolving the fused mass in water, acidulating with nitric 
acid, and adding a salt of baryta. Phosphorus is, in like manner, oxidized 
to phosphoric acid, the quantity of which is determined by precipitation in 
combination with sesquioxide of iron, or otherwise. 

Estimation of Chlorine. — The case of a volatile liquid containing chlorine 
is of most frequent occurrence, and may be taken as an illustration of the 
general plan of proceeding. The combustion with protoxide of copper 
must be very carefully conducted, and two or three inches of the anterior 
portion of the tube kept cool enough to prevent volatilization of the chloride 
of copper into the chloride of calcium tube. Chromate of lead is much 
better for the purpose. The chlorine is correctly determined by placing a 
email weighed bulb of liquid in a combustion-tube, which is afterwards 



EMPIRICAL AND RATIONAL FORMULAE. 329 

filled -with fragments of pure quick-lime. The lime is brought to a red- 
heat, and the vapour of the liquid driven over it, when the chlorine dis- 
places oxygen from the lime, and gives rise to chloride of calcium. When 
cold, the contents of the tube are dissolved in the dilute nitric acid, filtered, 
and the chlorine precipitated by nitrate of silver. 

EMPIRICAL AND RATIONAL FORMULA. 

A chemical formula is termed empirical when it merely gives the simplest 
possible expression of the composition of the substance to which it refers. 
A rational formula, on the contrary, aims at describing the exact composition 
of one equivalent, or combining proportion of the substance, by stating the 
absolute number of equivalents of each of its elements essential to that 
object, as well as the mere relations existing between them. The empirical 
formula is at once deduced from the analysis of the substance, reckoned to 
100 parts ; the rational requires in addition a knowledge of its combining 
quantity, which can only be obtained by direct experiment, by synthesis, or 
hy the careful examination of one or more of its most definite compounds. 
Farther, the rational may either coincide with the empirical formula, or it 
may be a multiple of the latter. 

Thus, the composition of acetic acid is expressed by the formula C 4 H 3 3 , 
which exhibits the simplest relations of the three elements, and at the same 
time expresses the quantities of these, in equivalents, required to make up 
an equivalent of acetic acid ; hence, it is both empirical and rational. On 
the other hand, the empirical formula of crystallized kinic acid is C 7 H 6 6 , 
while its rational formula, determined by its capacity of saturation, is double, 
or C 14 H l2 O l2 , otherwise written C 14 H 11 11 ,H0. In like manner, the empi- 
rical formula of the artificial alkaloids furf urine and amarine are respectively 
C 15 H 6 N0 3 and C 2l H 9 N. The equivalents of these substances, that is to say, 
the quantities required to form neutral salts with one equivalent of any well- 
defined monobasic acid, will, however, be expressed by the formulas C 3D H l2 
N 2 6 and C 42 H ig N 2 ; hence these latter deserve the name of rational. 

The deduction of an empirical formula from the ultimate analysis is very 
easy ; the case of sugar, already cited, may be taken as an example. This 
contains, according to the analysis, in 100 parts 

Carbon 41-98 

Hydrogen 6-43 

Oxygen 51-59 

10CKK) 

If each of these quantities be divided by the equivalent of the element, 
the quotients will express in equivalents the relations existing between them ; 
these are afterwards reduced to their simplest expression. This is the only 
part of the calculation attended with any difficulty ; if the numbers were rigidly 
correct, it would only be necessary to divide each by the greatest divisor 
common to the whole ; as they are, however, only approximative, something 
is of necessity left to the judgment of the experimenter, who is obliged to 
use more indirect means. 

41-98 51-59 

—£— = 6-99; 6-43; -g— = 6-44, 

or 699 eq. carbon, 643 eq. hydrogen, and 644 eq. oxygen. 
It will be evident, in the first place, that the hydrogen and oxygen are 
present in the proportions to form water, or as many equivalents of one as 
of the other. Again, the equivalents of carbon and hydrogen are neariv in 

28* 



330 



DETERMINATION OF THE DENSITY OE VAPOURS. 



the proportion of 12: 11, so that the formula Cj 2 H n O n appears likely to he 
correct. It is now easy to see how far this is admissible, by reckoning it 
back to 100 parts, comparing the result with the numbers given by the actual 
analysis, and observing whether the difference falls fairly in direction and 
amount within the limits of error of what may be termed a good experiment, 
viz., two or three-tenths per cent, deficiency in the carbon, and not more than 
one-tenth per cent, excess in the hydrogen. 

Carbon 6x12=72 

Hydrogen 11 eq. = ll 

Oxygen 8xH=88 

* 171 

171 : 72 = 100 : 42-11 
171 : 11 = 100 : 6-43 
171 : 88=100 : 51-46 

Organic acids and salt-radicals have their proper equivalents most fre- 
quently determined by an analysis of their lead- and silver-salts, by burning 
these latter with suitable precautions in a thin porcelain capsule, and noting 
the weight of the protoxide of lead or metallic silver left behind. If the 
protoxide of lead be mixed with globules of reduced metal, the quantity of 
the latter must be ascertained by dissolving away the oxide by acetic acid. 
Or the lead-salt may be converted into sulphate, and the silver-compound 
into chloride, and both metals thus estimated. An organic base, on the con- 
trary, or a basyle, has its equivalent fixed by the observation of the quantity 
of a mineral acid, or an inorganic salt-radical, required to form with it a 
combination having the characters of neutrality. 

DETERMINATION OP THE DENSITY OP VAPOURS. 

The determination of the specific gravity of the vapour of a volatile sub- 
stance is frequently a point of great importance, inasmuch 
Fig. 164. as it gives the means, in conjunction with the analysis, of 

representing the constitution of the substance by measure 
in a gaseous state. The following is a sketch of the plan 
of operation usually followed : — A light glass globe, fig. 
164, about three inches in diameter, is taken, and its neck 
softened and drawn out in the blowpipe-flame, as repre- 
sented in the figure, this is accurately weighed. About 
one hundred grains of the volatile liquid are then intro- 
duced, by gently warming the globe and dipping the point 
into the liquid, which is then forced upwards by the pres- 
sure of the air as the vessel cools. The globe is next 
firmly attached by wire to a handle, in such a manner that 
it may be plunged into a bath of boiling water or heated 
oil, and steadily held with the point projecting upwards. 
The bath must have a temperature considerably above 
that of the boiling-point of the liquid. The latter becomes 
rapidly converted into vapour, which escapes by the nar- 
row orifice, chasing before it the air of the globe. When 
the issue of vapour has wholly ceased, and the temperature of the bath, care- 
fully observed, appears pretty uniform, the open extremity of the point is 
hermetically sealed by a small blowpipe-flame. The globe is removed from 
the bath, suffered to cool, cleansed if necessary, and weighed, after which 
the neck is broken off beneath the surface of water which has been boiled 
and cooled out of contact of air, or better, mercury. The liquid enters the 
globe, and, if the expulsion of the air by the vapour has been complete, fills 




DETERMINATION OF THE DENSITY OF VAPOURS. 331 

it ; if otherwise, an air-bubble is left, -whose volume can be easily ascertained 
by pouring the liquid from the globe into a jar graduated to cubic inches, 
and then re-filling the globe, and repeating the same observation. The 
capacity of the vessel is thus at the same time known ; and these are all the 
data required. An example will render the whole intelligible. 

Determination of the density of the vapour of Acetone. 

Capacity of globe 31-61 cubic inches 

Weight of globe filled with dry air at 52° (11°-11C) 

and 30-24 inches barometer 2070-88 grains. 

Weight of globe filled with vapour at 212° (100°C) 

temp, of the bath at the moment of sealing the 

point, and 30-24 inches barometer 2076-81 grains. 

Residual air, at 45° (7°-22C), and 30-24 inches 

barometer 0-60 cubic inch. 



31-61 cub. inches of air at 52° and 30-24 in bar. = 32-36 cub. inches at 60° 

(15°-C) and 30 inch, bar., weighing 10-035 grains. 

Hence, weight of empty globe 2070-88—10-035=2060-845 grains. 



0-6 c. inch of air at 45°=0-8 c. inch at 212° ; weight of do. by calculation 

=0-191 grain. 
31-61—0-8 = 30-81 cubic inches of vapour at 212° and 30-24 in. bar., which, 

on the supposition that it could bear cooling to 60° without liquefaction, would, 

at that temperature, and under a pressure of 30 inch, bar., become reduced 

to 24-18 cubic inches. 
Hence, 

Weight of globe and vapour 2076-810 grains. 

,, residual air 0-191 

2076-619 
Weight of globe 2060-845 

Weight of the 24-18 cubic inches of vapour 15-774 

Consequently, 100 cubic inches of such vapour must 

weigh •. 65-23 

100 cubic inches of air, under similar circumstances, 

weigh 31-01 

65-23 

_ — =2-103, the specific gravity of the vapour in question, an 

31 '01 being unity. 



In the foregoing statement a correction has been, for the sake of simpli 
city, omitted^ which, in very exact experiments, must not be lost sight of, 
viz., the expansion and change of capacity of the glass globe by the elevated 
temperature of the bath. The density so obtained will be always en this 
account a little too high. 

The error to which the mercurial thermometer is, at high temperatures, 
liable, tends in the opposite direction. 



^32 DETERMINATION OF THE DENSITY OF VAPOURS. 

Tt is easy to compare the actual specific gravity of the vapour found in the 
manner above described with the theoretical specific gravity deduced from the 
formula of the substance : — 

The formula of acetone is C 3 H 3 0. In combining volumes this is repre- 
sented by 3 vols, of the hypothetical vapour of carbon, 3 vols, of hydrogen, 
and half a volume of oxygen. Or the weight of the unit of volume of ace- 
tone-vapour will be equal to three times the specific gravity of carbon-va- 
pour, three times that of hydrogen, and one-half that of oxygen added 
together, one volume of the compound vapour containing 6|- volumes of its 
components : 

3 vols, hypothetical vapour of carbon 0-4183x3 = 1-2549 

3 vols, hydrogen 0-0693x3=0-2079 

£ vol. oxygen =0-5528 

Theoretical specific gravity 2-0156 



CANE AND GRAPE-SUGAR. 33o 



SECTION I. 

NON-AZOTIZED BODIES OF THE SACCHARINE AND AMYLACEOUS 

GROUP. 



SUGAR, STARCH, GUM, LIGNIN, AND ALLIED SUBSTANCES. 

The members of tills remarkable and very natural group present several 
interesting cases of isomerism. They are characterized by their feeble 
aptitude to enter into combination, and also by containing, with perhaps one 
exception, oxygen and hydrogen in the proportions to form water. 

Table of Saccharine and Amylaceous Substances. 

Cane-sugar, crystallized C^H^O^ 

Cane-sugar, in combination C 24 Hj 8 18 

Grape-sugar, crystallized C^Hj^g 

Grape-sugar, in combination C^H^O^ 

Milk-sugar, crystallized C^H^O^ 

Milk-sugar, in combination C^H^Ojg 

Sugar from Secale cornutwn C 24 H 26 2 g 

Mannite , C 6 H 7 6 

Starch, unaltered, dried at 212° (100°C) C^H^O^ 

Amidin, or gelatinous starch ^24^20^20 

Dextrin, or gummy starch ^24^20^20 

Starch from Cetraria Islandica C^H^OgQ 

Inulin C24H 21 21 

Gum- Arabic C^H^O^ 

Gum-tragacanth C^H^O^ 

Lignin, or cellulose C 24 H 20 O 20 

Cane-sugar ; ordinary sugar, C^H^O^. — This most useful substance is 
found in the juice of many of the grasses, in the sap of several forest-trees, 
in the root of the beet and the mallow, and in several other plants. It is 
extracted most easily and in greatest abundance from the sugar-cane, culti- 
vated for the purpose in many tropical countries. The canes are crushed 
between rollers, and the expressed juice suffered to flow into a large vessel 
where it is slowly heated nearly to its boiling-point. A small quantity of 
hydrate of lime mixed with water is then added, which occasions the separa- 
tion of a coagulum consisting chiefly of earthy phosphates, waxy matter, a 
peculiar albuminous principle, and mechanical impurities. The clear liquid 
separated from the coagulum thus produced is rapidly evaporated in open 
pans heated by a fierce fire made with the crushed canes of the preceding 
year, dried in the sun and preserved for the purpose. When sufficiently 
concentrated the syrup is transferred to a shallow vessel, and left to crys- 
tallize, during which time it is frequently agitated in order to hasten the 
change and hinder the formation of large crystals. It is, lastly, drained 



334 CANE AND GRAPE-SUGAR. 

from the dark uncrystallizable syrup, or molasses, and sent into commerce, 
under the name of raio or Muscovado sugar. The refining of this crude pro- 
duct is effected by re-dissolving it in water, adding a quantity of albumen in 
the shape of serum of blood or white of egg, and sometimes a little lime- 
water, and heating the whole to the boiling-point ; the albumen coagulates, 
and forms a kind of net-work of fibres, which inclose and separate from the 
liquid all mechanically suspended impurities. The solution is decolorized by 
filtration through animal charcoal, evaporated to the crystallizing-point, and 
put into conical earthen moulds, where it solidifies, after some time, to a 
confusedly-crystalline mass, which is drained, washed with a little clean 
syrup, and dried in a stove ; the product is ordinary loaf-sugar. When the 
crystallization is allowed to take place quietly and slowly, sugar-candy re- 
sults, the crystals under these circumstances acquiring large volume and 
regular form. The evaporation of the decolorized syrup is best conducted 
in strong close boilers exhausted of air ; the boiling-point of the syrup is 
reduced in consequence from 230° (110°C) to 150° (65°-5C) or below, and 
and the injurious action of the heat upon the sugar in great measure pre- 
vented. Indeed, the production of molasses in the rude colonial manufacture 
is chiefly the result of the high and long-continued heat applied to the cane- 
juice, and might be almost entirely prevented by the use of vacuum-pans, 
the product of sugar being thereby greatly increased in quantity, and so far 
improved in quality as to become almost equal to the refined article. 

In many parts of the continent of Europe sugar is manufactured on a large 
scale from beet-root, which contains about 8 per cent, of that substance. The 
process is far more complicated and troublesome than that just described, 
and the product much inferior. When refined, however, it is scarcely to be 
distinguished from the preceding. The inhabitants of the Western States of 
America prepare sugar in considerable quantity from the sap of the sugar- 
maple, Acer saccharinum, which is common in those parts. The tree is tapped 
in the spring by boring a hole a little way into the wood, and inserting a 
small spout to convey the liquid into a vessel placed for its reception. This 
is boiled down in an iron pot, and furnishes a coarse sugar, which is almost 
wholly employed for domestic purposes, but little finding its way into com- 
merce. 

Pure sugar slowly separates from a strong solution in large, transparent 
colourless crystals, having the figure of a modified oblique rhombic prism. 
It has a pure, sweet taste, is very soluble in water, requiring for solution 
only one-third of its weight in the cold, and is also dissolved by alcohol, but 
with more difficulty. When moderately heated it melts, and solidifies on 
cooling to a glassy amorphous mass, familiar under the name of barley sugar: 
at a higher temperature it blackens and suffers decomposition ; and the same 
effect is produced, as already remarked, by long-continued boiling of the 
aqueous solution, which loses its faculty of crystallizing and acquirer colour. 
The crystals have a specific gravity of 1-6, and are unchanged in the air. 

The deep brown soluble substance called caramel, used for colouring spirits, 
and other purposes, is a product of the action of heat upon cane-sugar. It 
contains C 2 4H 18 0i8, and is isomeric with cane-sugar in combination. 

The following is the composition assigned to the principal compounds of 
cane-sugar by M. Peligot, who has devoted much attention to the subject. 1 

Crystallized cane-sugar C 24 H 18 ls -j-4IIO 

Compound of sugar with common salt C 24 H, 8 ls -j-NaCl-}-3IIO 

Compound of sugar with baryta C 24 H 18 18 -f2BaO-f4HO 

Compound of sugar with lime C 24 H 18 0, 8 -|-2CaO-}-4HO 

Compound of sugar with protoxide of lead .... C 24 II 18 18 -|-4PbO 

1 Ann. Ckim. et Phys. lxyii. 113. 



CANE AND GRAPE-SUGAR. 335 

The compounds with baryta and lime are prepared by digesting sugar at 
a gentle heat -with the hydrates of the earths. The lime-compound has a 
bitter taste, andis more soluble in cold water than in hot. Both are readily 
decomposed by carbonic acid, crystals of carbonate of lime being occasion- 
ally produced. The combination with protoxide of lead is prepared by mix- 
ing sugar with a solution of acetate of lead, adding excess of ammonia, and 
drying the white insoluble product out of contact with air. The compound 
with common salt is crystallizable, soluble, and deliquescent. 

Grape-sugar ; glucose ; sugar of fruits, C 24 H 28 28 . — This variety of 
sugar is very abundantly diffused through the vegetable kingdom ; it may be 
extracted in large quantity from the juice of sweet grapes, and also from 
honey, of which it forms the solid crystalline portion, by washing with cold 
alcohol, which dissolves the fluid syrup. It may also be prepared by arti- 
ficially modifying cane-sugar, starch, and woody fibre, by processes presently 
to be described. The appearance of this substance, to an enormous extent, 
in the urine, is the most characteristic feature of the disease called diabetes. 

Grape-sugar is easily distinguished by several important peculiarities from 
cane-sugar: it is much less sweet, and less soluble in water, requiring 1£ 
parts of tlje cold liquid for solution. Its mode of crystallization is also 
completely different ; instead of forming, like cane-sugar, bold, distinct crys- 
tals, it separates from its solutions in water and alcohol in granular warty 
masses, which but seldom present crystalline faces. When pure, it is nearly 
white. When heated, it melts, and loses 4 eq. of water, and at a higher 
temperature blackens and suffers decomposition. Grape-sugar combines 
with difficulty with lime, baryta, and oxide of lead, and is converted into a 
brown or black substance when boiled with solution of caustic alkali, by 
which cane-sugar is but little affected. It dissolves, on the contrary, in 
strong, oil of Vitriol without blackening, and gives rise to a peculiar com- 
pound acid, whose baryta-salt is soluble. Cane-sugar is, under these cir- 
cumstances, instantly changed to a black mass resembling charcoal. 

When solutions of cane and grape-sugar are mixed with two separate por- 
tions of solution of sulphate of copper, and caustic potassa added in excess 
to each, deep blue liquids are obtained, which, on being heated, exhibit dif- 
ferent characters ; the one containing cane-sugar is at first but little altered ; 
a small quantity of red powder falls after a time, but the liquid long retains 
its blue tint : with the grape-sugar, on the other hand, the first application 
of heat throws down a copious greenish precipitate, which rapidly changes 
to scarlet, and eventually to dark red, leaving a nearly colourless solution. 
This is an excellent test for distinguishing the two varieties of sugar, or dis- 
covering an admixture of grape with cane-sugar. 

Grape-sugar unites with common salt, forming a soluble compound of 
sweetish saline taste, which crystallizes in a regular and beautiful manner. 

Compounds of Grape-sugar, according to Peligot. 

Crystalline grape-sugar dried in the air C 24 H 21 21 -|-7HO 

The same, dried at 266° (130°C) C^HgjO^-f-SHO 

Compound of grape-sugar with common salt C^H^O^-f-NaCl-f-SHO 

The same, dried at 266° (130°C) C^H^O^-f NaCl-f-2HO 

Compound of grape-sugar with baryta C 24 H 21 21 -(-3BaO--f 7HO 

Compound of grape-sugar with lime C 24 H 21 21 -}-3CaO-f-7HO 

Compound of grape-sugar with protoxide of lead C^H^O^-j-oTbO 

Sulphosaccharic Acid, C 24 H 20 O 20 ,SO 3 . — Melted grape-sugar is cautiously 
mixed with concentrated sulphuric acid, the product dissolved in water, and 
neutralized with carbonate of baryta ; sulphate of baryta is formed together 
with a soluble sulphosaccharate of that earth, from which the acid itself 



336 CANE AND GRAPE-SUGAR. 

may be afterwards eliminated. It is a sweetish liquid, forming a variety of 
soluble salts, and very prone to decompose into sugar and sulphuric acid. 

Action of dilute Acids upon Sugar. — Cane-sugar dissolved in dilute sulphuric 
acid is gradually but completely converted, at the common temperature of 
the air, into grape-sugar. The same solution, when long boiled, yields a 
brownish-black and nearly insoluble substance, which is a mixture of two 
distinct bodies, one having the appearance of small shining scales, and the 
other that of a dull brown powder. The first, called by Boullay and Mala- 
guti ulmin, and by Liebig sacchulmin, is insoluble in ammonia and alkalis ; 
the second, ulmic acid, the sacchulmic acid of Liebig, dissolves freely, yielding 
dark brown solutions precipitable by acids. By long-continued boiling with 
water, sacchulmic acid is converted into sacchulmin. Both these substances 
have the same composition, expressed by the empirical formula C 2 HO. Hy- 
drochloric acid in a dilute state, produces the same effects. 1 

Action of Alkalis upon Sugar. — When lime or baryta is dissolved in a solu- 
tion of grape-sugar, and the whole left to itself several weeks in a close 
vessel, the alkaline reaction will be found to have disappeared from the for- 
mation of an acid substance. By mixing this solution with basic acetate of 
lead, a voluminous white precipitate is obtained, which, when decomposed 
by sulphuretted hydrogen, yields sulphide of lead, and the new acid, to which 
the term kalisaccharic or glucic is applied. Glucic acid is very soluble and 
deliquescent, has a sour taste and acid reaction : its salts, with the exception 
of that containing protoxide of lead, are very soluble. It contains C g H 5 5 . 
When grape-sugar is heated in a strong solution of potassa, soda, or baryta, 
the liquid darkens, and at length assumes a neai'ly black colour. The addi- 
tion of an acid then gives rise to a black flocculent precipitate of a substance 
called melasinic acid, containing C 24 H l2 O 10 . Cane-sugar long-boiled with 
alkalis undergoes the same changes, being probably first converted into 
grape-sugar. 

Sugar prom ergot of rye. — This variety of sugar, extracted by alcohol 
from the ergot, crystallizes in transparent colourless prisms, which have a 
sweet taste, and are very soluble in water. It differs from cane-sugar in not 
reducing the acetate of copper when boiled with a solution of that substance. 
It contains C 24 H 26 26 . 

Sugar of diabetes insipidus. — A substance having the other properties 
of a sugar, but destitute of sweet taste, has been described by M. Th^nard 
as having been obtained from the above-mentioned source. It was capable 
of furnishing alcohol by fermentation, and of suffering conversion into grape- 
sugar by dilute sulphuric acid. Its composition is unknown. 

Liquorice-sugar ; glycyrrhizin. — The root of the common liquorice 
yields a large quantity of a peculiar sweet substance, which is soluble in 
water, but refuses to crystallize ; it is remarkable for forming with acids 
compounds which have but sparing solubility. Glycyrrhizin cannot be made 
to ferment. The formula of this substance is not definitely settled. 

Sugar of milk; lactin, C 24 H 24 21 . — This curious substance is an impor- 
tant constituent of milk ; it is obtained in large quantities by evaporating 
whey to a syrupy state, and purifying the lactin, which slowly crystallizes out 
by animal charcoal. It forms white, translucent, four-sided prisms, of great 

1 Under the names ulmin and ulmic acid (humin and luimic acid, crenic and apo-crenic acids.) 
have been confounded a number of brown or black uncrystallizable substances, produced by the 
action of powerful chemical agents upon sugar, lignin, Ac, or generated by the putrefactive 
d?cay of vegetable fibre. Common garden mould, for example, treated with dilute, boiling 
solution of caustic potassa, yields a deep brown solution, from which acids precipitate a floc- 
culent, brown substance, having but a slight degree of solubility in water. This is generally 
jailed ulmic or humic acid, and its origin ascribed to the reaction of the alkali on the ulmin 
or humus of the soil. It is known that these bodies differ exceedingly in composition; they 
»re too indftfinite to admit of ready investigation. 






MANNITE— STARCH. 837 

hardness. It is slow and difficult of solution in cold water, requiring for 
that purpose 5 or 6 times its weight ; it has a feeble sweet taste, and in the 
solid state feels gritty between the teeth. When heated, it loses water, and at 
a high temperature blackens and decomposes. Milk-sugar forms several com- 
pounds with protoxide of lead, and is converted into grape-sugar by boiling 
with dilute mineral acids. It is not directly fermentable, but can be made, 
under particular circumstances, to furnish alcohol. 

Manna-sugar; mannite, C 6 H 7 6 or C 12 H 14 0i 2 . — This is the chief compo- 
nent of manna, an exudation from a species of ash ; it is also found in the 
juice of certain other plants, and in several sea-weeds, and may be formed 
artificially from ordinary sugar by a peculiar kind of fermentation. It is 
best prepared by treating manna with boiling alcohol, and filtering the solu- 
tion whilst hot ; the mannite crystallizes on cooling in tufts of slender colour- 
less needles. It is fusible by heat without loss of weight, is freely soluble 
in water, possesses a powerfully sweet taste, and has no' purgative properties. 
Mannite -refuses to ferment. This substance combines with sulphuric acid, 
giving rise to a new acid, the composition of which is not yet definitely 
established. It is likewise acted on by concentrated nitric acid. The product 
of this action will be noticed farther on. The substance formerly described 
as mushroom-sugar is merely mannite. 

Starch ; fecula. — This is one of the most important and widely diffused 
of the vegetable proximate principles, being found to a greater or less extent 
in every plant. It is most abundant in certain roots and tubers, and in soft 
stems : seeds often contain it in large quantity. From these sources the 
fecula can be obtained by rasping or grinding to pulp the vegetable structure, 
and washing the mass upon a sieve, by which the torn cellular tissue is re- 
tained, while the starch passes through with the liquid, and eventually settles 
down from the latter as a soft, white, insoluble powder, which maybe washed 
with cold water, and dried with very gentle heat. Potatoes treated in this 
manner yield a large proportion of starch. Starch from grain may be pre- 
pared in the same manner, by mixing the meal with water to a paste, and 
washing the mass upon a sieve : a nearly white, insoluble substance called 
gluten or glutin remains behind, which contains a large proportion of nitrogen. 
The glutin of wheat-flour is extremely tenacious and elastic. The value of 
meal as an article of food greatly depends upon this substance. Starch from 
grain is commonly manufactured on the large scale by steeping the material 
in water for a considerable period, when the lactic acid, always developed 
under such circumstances from the sugar of the seed, disintegrates, and in 
part dissolves the azotized matter, and greatly facilitates the mechanical 
separation of that which remains. A still more easy and successful process 
has lately been introduced, in which a very dilute solution of caustic soda, 
containing about 200 grains of alkali to a gallon of liquid is employed with 
the same view. Excellent starch is thus prepared from rice. Starch is inso- 
luble in cold water, as indeed its mode of preparation sufficiently shows ; it 
is equally insoluble in alcohol and other liquids which do not effect its de- 
composition. To the naked eye it presents the appearance of a soft, white, 
and often glistening powder ; under the microscope it is seen to be altogether 
destitute of crystalline structure, but to possess, on the contrary, a kind of 
organization, being made up of multitudes of little rounded transparent 
bodies, upon each of which a series of depressed parallel rings surrounding 
a central spot or hilum, may often be traced. The starch-granules from dif- 
ferent plants vary both in magnitude and form ; those from the Canna coc- 
cinea, or tous les mois, and potato being largest ; and those from wheat, and 
the cereals in general, very much smaller. The figure on the next page 
(Fig. 165) will set ?e to convey an idea of the appearance of the granules of 
potato-starch, highly magnified. 
29 



338 



DEXTRIN, 




When a mixture of starch and water is heated 
to near the boiling-point of the latter, the granules 
burst and disappear, producing, if the proportion 
of starch be considerable, a thick gelatinous mass, 
very slightly opalescent from the shreds of very 
fine membrane, the envelope of each separate 
granule. By the addition of a large quantity of 
water, this gelatinous starch, or amidin, may be 
so far diluted as to pass in great measure through 
filter-paper. It is very doubtful, however, how 
far the substance itself is really soluble in water, 
at least when cold ; it is more likely to be merely 
suspended in the liquid in the form of a swollen, 
transparent, insoluble jelly, of extreme tenuity. 
Gelatinous starch, exposed in a thin layer to a 
dry atmosphere, becomes converted into a yel- 
lowish, horny substance, like gum, which, when 
put into water, again softens and swells. 

Thin gelatinous starch is precipitated by many of the metallic oxides, as 
lime, baryta, and protoxide of lead, and also by a large addition of alcohol. 
Infusion of galls throws down a copious yellowish precipitate containing 
tannic acid, which re-dissolves when the solution- is heated. By far the 
most characteristic reaction, however, is-tM't with free iodine, which forms 
with starch a deep indigo-blue compound, whicli 'appears to dissolve in ptire 
water, although it is insoluble in solutions containing free acid or saline 
matter. The blue liquid has its colours^destroyed^by heat, temporarily if 
the heat be quickly withdraw, and permanently If. the boiling be long con- 
tinued, in which case the compound is decomposed, and the iodine volati- 
lized. Starch in the dry state, put in£5' iodine-w&ter, acqurres a purplish- 
black colour. .;> 

The unaltered and the gelatinOus-^starch, in a djpi'ed state, have the same 
composition, namely, C 24 H 2o 2o : a compound of~s'&rcli and protoxide of 
lead was found to contain, wffengfricfd at 212 o ..(lQ0 o .C), C 24 H 20 O 20 -f4PbO. 

Dextrin. — When gelatinous starch is boiled. with a small quantity of 
dilute sulphuric, hydrochh»jt£Tor, incleVl, ali'njist any acid, it speedily loses 
its consistency, and becomes rain and limpid^ from .having suffered conver- 
sion into a soluble substanc^Tese-mbiing gum> called .dextrin. 1 The experi- 
ment is most convenientlyniade^jv-ith sulphuric a«id, which may be after- 
wards withdrawn by saturation j$£th chalk. The "liquid filteredVfrom the 
nearly insoluble gypsum, may then be evaporated in a water-bath to dry- 
ness. . The result, is a * gum-like ; mags, destitute of" crystalline structure, 
soluble in cold . wate*?* and. precipifabjle from its solution Jby alcohol, and 
capable of combining with..pj"otoxide'of lead. 

When the ebullition wl't^ the dilute acid is continued for a considerable 
period, the dextrin* first fdrmed undergoes a farther change, and becones 
converted into grape-sttgar, whLeh can be thus artificially produced- with the 
greatest facility. The length &£ time required for this remarkable change 
depends upon the quantity of acid present; if the latter be very, small, it is 
necessary to continue the boiling many successive-- hours, replacing the 
water which evaporates. With a larger proportion of acid, the conversion is 
much more speedy. A mixture of 15 parts potato-starch,. 60 parts water, 
and G parts sulphuric acid, may be kept boiling for about. four hours; 'the' 
liquid neutralized with chalk, filtered, and rapidly evaporated to a small 



1 From its a'tion 
hand. 



:u polarized light, twisting the plane of polarization towards the right 



DEXTRIN STARCn INULIN. 339 

bulk. By digestion "with animal charcoal and a second filtration much of 
the colour will be removed, after which the solution may be boiled down to 
a thin syrup and left to crystallize ; in the course of a few days it solidifies 
to a mass of grape-sugar. There is another method of preparing this sub- 
stance from starch which deserves particular notice. Germinating seeds, 
and buds in the act of development, are found to contain a small quantity 
of a peculiar azotized substance, formed at this particular period from the 
glutiu or vegetable albuminous matter, to which the name diastase is given. 
This substance possesses the same curious property of effecting the conver- 
sion of starch into dextrin, and ultimately into grape-sugar, and at a much 
lower temperature than that of ebullition. A little infusion of malt, or ger- 
minated barley, in tepid water, mixed with a large quantity of thick gela- 
tinous starch, and the whole maintained at 160° (71 °C), or thereabouts, 
occasions complete liquefaction in the space of a few minutes from the pro- 
duction of dextrin, which in its turn becomes in three or four hours con- 
verted into sugar. If a greater degree of heat be employed, the diastase is 
coagulated and rendered insoluble and inactive. , Very little is known 
respecting diastase itself; it seems very much to resemble vegetable albumin, 
but has never been got in a state of purity. 

The change of starch or dextrin into sugar, whether produced by the 
action of dilute acid or by diastase, takes place quite independently of the 
oxygen of the air, and is unaccompanied by any secondary product. The 
acid takes no direct part in the reaction ; it may, if not volatile, be all with- 
drawn without loss after the experiment. The whole affair lies between the 
starch and the elements of water ; a fixation of the latter occuring in the 
new product, as will be seen at once on comparing their composition. -- The 
sugar, in fact, so produced, ve~y sensibly exceeds in weight the starch: em- 
ployed. Dextrin itself has exactly the same composition as the original 
starch. - ' 

Dextrin is used in L he arts as a substitute for gum; it is sometimes made 
in the manner above described, but more frequently by heating dry potato- 
starch to 400° (204°'5C), by which it acquires a yellowish" tint and becomes 
soluble in cold water. It is sold in this state under the appellation of British 
Gum. 

Starch is an important article of food, especially when associated, as in 
ordinary meal, with albuminous substances. Arrow-root, and the fecula of 
the Canna coccinea, are very pure varieties, employed as articles of diet ; 
arrow-root is obtained from the Maranta arundinacea, cultivated in the West 
Indies ; it is with difficulty distinguished from potato-starch. Tapioca is 
prepared from the root of the Iatropha manihot, being thoroughly purified 
from its poisonous juice. Cassava is the same substance modified while 
moist by heat. Sago is made from the soft central portion of the stem of a 
palm-tree. 

Starch from Iceland Moss. — The lichen called Cetraria Islandica, puri- 
fied by a little cold solution of potassa from a bitter principle, yields when 
boiled in water a slimy and nearly colourless liquid, which gelatinizes on 
cooling, and dries up to a yellowish amorphous mass, which does not dissolve 
in cold water, but merely softens and swells. A solution of this substance 
in warm water is not affected by iodine, although the jelly, on the contrary, 
is rendered blue. It is precipitated by alcohol, acetate of lead, and infusion 
of galls, and is converted by boiling with dilute sulphuric acid into grape- 
sugar. According to Mulder, linen-starch likewise contains C 24 H 20 O 20 . The 
jelly from certain algce, as that of Ceylon, and the so-called Carragheen moss, 
closely resembles the above. 

Inultn. — This substance, which differs from common starch in some im 
portant particulars, is found in the root of the Inula helenium, the Helianthua 



340 GUM. 

iuberosus, the dahlia, and several other plants ; it may be easily obtained by 
■washing the rasped root on a sieve, and allowing the inulin to settle down 
from the liquid ; or by cutting the root into thin slices, boiling these in 
water, and filtering while hot; the inulin separates as the solution cools. It 
is a white, amorphous, tasteless substance, nearly insoluble in cold water, 
but freely dissolved by the aid of heat ; the solution is precipitated by alco- 
hol, but not by acetate of lead or infusion of galls. Iodine communicates a 
brown colour. Inulin has been analyzed by Mr. Parnell, who finds it to 
contain, when dried at 212° (100°C), C 24 H 2 ,0 21 . 

Gum. — Gum- Arabic, which is the produce of an acacia, may be taken as 
the most perfect type of this class of bodies. In its purest and finest con- 
dition, it forms white or slightly yellowish irregular masses, which are des- 
titute of crystalline structure, and break with a smooth conchoidal fracture. 
It is soluble in cold water, forming a viscid, adhesive, tasteless solution, 
from which the pure soluble gummy principle, or arabin, is precipitated by 
alcohol and by basic acetate of lead, but not by the neutral acetate. 1 Ara- 
bin is composed of 0241122022, and is consequently isomeric with crystallized 
cane-sugar. 

Mucilage, so abundant in linseed, in the roots of the mallow, in salep, the 
fleshy root of Orchis mascula, and in other plants, differs in some respects 
from the foregoing, although it agrees in the property of dissolving in cold 
water. The solution is less transparent than that of gum, and is precipi- 
tated by neutral acetate of lead. Gum Iragacanth is chiefly composed of a 
kind of mucilage to which the name bassorin has been given, and which 
refuses to dissolve in water, merely softening and assuming a gelatinous 
aspect. It is dissolved by caustic alkali. Cerasin is the term given to the 
insoluble portion of the gum of the cherry-tree ; it resembles bassorin. The 
composition of these various substances has been carefully examined by M. 
Schmidt, who finds that it closely agrees with that of starch. Mucilage in- 
variably contains hydrogen and oxygen in the proportion in which they form 
water, and when treated with acid, yeild grape-sugar. 

Pectin, or the jelly of fruits, is, in its physical properties, closely allied to 
the foregoing bodies. It may be extracted from various vegetable juices by 
precipitation by alcohol. It forms, when moist, a transparent jelly, soluble 
in water, and tasteless, which dries up to a translucent mass. It is to this 
substance that the firm consistence of currant and other fruit jellies is 
to be ascribed. According to M. Fremy, the composition of pectin is 
C 64 TI 48 64 . By ebullition with water and with dilute acids it is changed into 
two isomeric modifications, to which the names parapectin and metapectin 
have been given. In contact with bases, these three substances become 
converted into pectic acid, which, except that it possesses feeble acid proper- 
ties, and is insoluble in water, resembles in the closest manner pectin itself. 
By long boiling with solution of caustic alkali, a farther change is produced, 
and a new acid, the metapectic, developed, which does not gelatinize. The 
salts of these two acids are incapable of crystallizing. Their composition 
is represented by the following formulae : — 

Pectic acid 2HO,C 32 H 20 O 28 

Metapectic acid 2IIO,C 24 Hj 5 2 

Much doubt still exists respecting the composition of the various bodies of 
the pectin-series ; they do not appear, from the analyses yet made, to con 

1 The precipitate produced by sub-salts of lead is a compound of arabine and oxide of lead, 
CiiIl2202i-+-2PbO. By the action of very dilute sulphuric acid arabine ia slowly changed into 
dextrine, and by prolonged contact into glucose. .Nitric acid decomposes gum and produces 
tiist mucic and ultimately oxalic acid. — 11. B. 



OXALIC ACID. 841 

tain oxygen and hydrogen in equal equivalents, and consequently scarcely 
belong to the starch-group. 

Lignin; cellulose. — This substance constitutes the fundamental mate- 
rial of the structure of plants ; it is employed in the organization of cells, 
and vessels of all kinds, and forms a large proportion of the solid parts of 
every vegetable. It must not be confounded with ligneous or ivoodij tissue, 
which is in reality cellulose, with other substances superadded, which encrust 
the walls of the original membraneous cells, and confer stiffness and inflex- 
ibility. Thus woody tissue, even when freed as much as possible from 
colouring matter and resin by repeated boiling with water and alcohol, 
yields on analysis a result indicating an excess of hydrogen above that 
required to form water with the oxygen, besides traces of nitrogen. Pure 
cellulose, on the other hand, is a ternary compound of carbon and the ele-- 
ments of water, closely allied in composition to starch, if not actually 
isomeric with that substance. 1 • 

The properties of lignin may be conveniently studied in fine linen or 
cotton, which are almost entirely composed of the body in question, the 
associated vegetable principles having been removed or destroyed by the 
variety of treatment to which the fibre has been subjected. Pure lignin is 
tasteless, insoluble in water and alcohol, and absolutely innutritious ; it is 
not sensibly affected by boiling water, unless it happen to have been derived 
from a soft or imperfectly developed portion of the plant, in which case it is 
disintegrated and rendered pulpy. Dilute acids and alkalis exert but little 
action on lignin, even at a boiling temperature ; strong oil of vitriol converts 
it, in the cold, into a nearly colourless, adhesive substance, which dissolves 
in water, and presents the character of dextrin. This curious and interest- 
ing experiment may be conveniently made by very slowly adding concen- 
trated sulphuric acid to half its weight of lint, or linen cut into small shreds, 
taking care to avoid any rise of temperature, which would be attended with 
charring or blackening. The mixing is completed by trituration in a mor- 
tar, and the whole left to stand a few hours ; after which it is rubbed up 
with water, and warmed, and filtered from a little insoluble matter. The 
solution may then be neutralized with chalk, and again filtered. The gummy 
liquid retains lime, partly in the state of sulphate, and partly in combina- 
tion with a peculiar acid, composed of the elements of sulphuric or hypo- 
sulphuric acid, in union with those of the lignin, to which the name sulpho- 
lignic acid is given. If the liquid, previous to neutralization, be boiled 
during three or four hours, and the water replaced as it evaporates, the 
dextrin becomes entirely changed to grape-sugar. Linen rags may, by 
these means, be made to furnish more than their own weight of that sub- 
stance. 

Lignin is not coloured by iodine. 



PRODUCTS ARISING .FROM THE ALTERATION OF THE PRECEDING SUBSTANCES 
BY CHEMICAL AGENTS. 

ACTION OF NITRIC ACID. 

Oxalic Acid, C 2 3 .HO-|-2HO. — This important compound occurs ready 
formed in several plants, in combination with potassa as an acid salt, or 
with lime. It is now manufactured in large quantities as an article of 

1 Dumas, Chimie appliqu€e aux Arts, vi. 5. 
29* 



342 OXALIC ACID. 

commerce, by the action of nitric acid on sugar, starch, and dextrin. With 
the exception of gum and sugar of milk, ■which yield another product, all 
the substances comprehended in the saccharine and starch group furnish 
oxalic acid, as the chief and characteristic result of the long-continued 
action of moderately strong nitric acid at an elevated temperature. 

One pai*t of sugar is gently heated in a retort with 5 parts of nitric acid 
of sp. gr. 1-42, diluted with twice its weight of water; copious red fumes 
are disengaged, and the oxidation of the sugar proceeds with violence and 
rapidity. When the action slackens, heat may be again applied to the 
vessel, and the liquid concentrated, by distilling off the superfluous nitric 
acid, until it deposits crystals on cooling. These are drained, re-dissolved 
in a small quantity of hot water, and the solution set aside to cool. The 
acid separates from a hot solution in colourless, transparent crystals derived 
from an oblique rhombic prism, which contain three equivalents of water, 
one of these being basic and inseparable, except by substitution ; the other 
two may be expelled by a very gentle heat, the crystals crumbling down to 
a soft white powder, which may be sublimed in great measure without 
decomposition. The crystallized acid, on the contrary, is decomposed by a 
high temperature into carbonic and formic acids and carbonic oxide, without 
solid residue. 

The crystals of oxalic acid dissolve in 8 parts of water at 60° (15°-5C), and 
in their own weight, or less, of hot water ; they are also soluble in spirit. 
The aqueous solution has an intensely sour taste and most powerful acid re- 
action, and is highly poisonous. The proper antidote is chalk or magnesia. 
Oxalic acid is decomposed by hot oil of vitriol into a mixture of carbonic 
oxide and carbonic acid ; it is slowly converted into carbonic acid by nitric 
acid, whence arises a considerable loss in the process of manufacture. The 
binoxides of lead and manganese effect the same change, becoming reduced 
to protoxides, which combine with the unaltered acid. 

Oxalic acid is formed from sugar by the replacement of the whole of its 
hydrogen by an equivalent quantity of oxygen. 

1 eq. sugar =C 24 H 18 ls \ __ (1 2 eq. oxalic acidznzC^ 33 
36 eq. oxygen= 36 / \ 18 eq. water = H 18 18 

C 2 4Hig0 54 ^24^18^54 

The most important salts of oxalic acid are the following: — 

Neutral oxalate of fotassa, K0,C 2 3 -f-H0. — This is prepared by 
neutralizing oxalic acid by carbonate of potassa. It crystallizes in transpa- 
rent rhombic prisms, which become opaque and anhydrous by heat, and dis- 
solve in 3 parts of water. Oxalate of potassa is often produced when a 
variety of organic substances are cautiously heated with excess of caustic 
alkali. 

Binoxalate of potassa, KO,2C 2 3 -4-3110. — Sometimes called salt of 
sorrel, from its occurrence in that plant. This, or the substance next to be 
mentioned, is found also in the rumez and oxalis acetosella, and in the garden 
rhubarb, associated with malic acid. It is easily prepared by dividing a so- 
lution of oxalic acid, in hot water, into two equal portions, neutralizing one 
with carbonate of potassa, and adding the other; the salt crystallizes on 
cooling, in colourless rhombic prisms. The crystals have a sour taste, and 
require 40 parts of cold, and G of boiling water for solution. 

Quadroxaiate of totassa, KO,4C 2 3 -f- 7HO. — Prepared by a process 
similar in principle to that last described. The crystals are modified octahe- 
drons, and are less soluble than those of the binoxalate, which the salt in 
other respects resembles. 

Oxalate of soda, NaO,C 2 3 , has but little solubility; a binoxalate exists. 



OXALIC ACID. 343 

Oxalate of ammonia, NH 4 0,C 2 3 -4-HO. — This beautiful salt is prepared 
by neutralizing by carbonate of ammonia a hot solution of oxalic acid. It 
crystallizes in long, colourless, rhombic prisms, which effloresce in dry air 
from loss of water of crystallization. They are not very soluble in cold 
water, but freely dissolve by the aid of heat. Oxalate of ammonia is of great 
value in analytical chemistry, being employed to precipitate lime from its 
solutions. When oxalate of ammonia is heated in a retort, it is completely 
decomposed, yielding water, ammonia and carbonate of ammonia, cyanogen 
and carbonic acid gases, and a small quantity of a peculiar greyish white 
sublimate. The latter bears the name of oxamide ; it is a very remarkable 
body, and forms the type of a large class of substances containing the ele- 
ments of an ammoniacal salt, minus those of water. Oxamide is composed 
of C 2 II 2 N0 2 , i.e., NH 4 0,C 2 3 — 2HO, or the elements of 1 eq. amidogen, and 
2 eq. carbonic oxide. It is insoluble in water and alcohol: when boiled with 
an alkali it furnishes an oxalate of the base, and ammonia, which is expelled; 
and when heated with an acid, it produces an ammoniacal salt. When treated 
with nitrous acid it likewise reproduces oxalic acid, pure nitrogen being 
evolved C 2 H 2 N0 2 -fN0 3 =C 2 3 ,HO-fHO-f 2N. Oxamide is the representa- 
tive of a tolerably large class of bodies having very analogous chemical rela- 
tions, and apparently a common constitution. Oxamide is obtained purer 
and more abundantly from oxalic ether ; its preparation will be found des- 
cribed under the head of that substance. Oxalate of ammonia, when dis- 
tilled with anhydrous phosphoric acid, loses four equivalents of water and 
yields a considerable quantity of cyanogen, NH 4 0,C 2 3 — 4HO = C 2 N. There 
are, however, other compounds simultaneously produced. 

The binoxalate of ammonia is still less soluble than the oxalate. When 
this salt is heated in an oil-bath to 450° (232° -2C), among other products an 
acid called the oxamic is generated, containing C 4 H-NO £ ,HO, i.e., NH 4 0, 
C 2 3 ,HO,C 2 $ — 2 HO, and may be viewed as a compound of oxalic acid with 
oxamide. It forms soluble compounds with lime and baryta. When heated 
with alkalis it yields ammonia and oxalate; hot oil of vitriol resolves it into 
carbonic oxide and carbonic acid ; and water converts it, at a boiling tem- 
perature, into binoxalate of ammonia. Oxamic acid too, is interesting as the 
type of a very large class of similarly constructed compounds. 

Oxalate of lime, CaO,C 2 3 -j-2HO. — This compound is formed whenever 
oxalic acid or an oxalate is added to a soluble salt of lime ; it falls as a white 
powder, which acquires density by boiling, and is but little soluble in hydro- 
chloric, and entirely insoluble in acetic acid. Nitric acid dissolves it easily. 
When dried at 212° (100°C) it retains an equivalent of water, which may be 
driven off by a rather higher temperature. Exposed to a red-heat in a close 
vessel, it is converted into carbonate of lime, with escape of carbonic oxide. 

The oxalates of baryta, zinc, manganese, protoxide of iron, copper, nickel, and 
cobalt, are nearly insoluble in water; that of magnesia is sparingly soluble, 
and that of the scsquioxide of iron freely soluble. The double oxalate of chro- 
mium and potassa, made by dissolving in hot water 1 part bichromate of po- 
tassa, 2 parts binoxalate of potassa, and 2 parts crystallized oxalic acid, is 
one of the most beautiful salts known. The crystals appear black by re- 
flected light from the intensity of their colour, which is pure deep blue ; 
they are very soluble. The salt contains 3(KO,C 2 3 )-f Cr 2 8 ,3C a 3 -f HO. A 
corresponding compound containing sesquioxide of iron has been formed ; it 
crystallizes freely, and has a beautiful green colour. 

Saccharic acid, C 6 H 4 7 ,HO. — This substance was once thought to b? 
identical with malic acid, which is not the case; it is formed by the action 
of dilute nitric acid on sugar, and is often produced in the preparation of 
oxalic acid, being, from its superior solubility, found in the mother-liquor 
from which the oxalic acid has crystallized. It may be made by heating to- 



844 i saccharic acid. 

gether 1 part sugar, 2 parts nitric acid, and 10 parts water. When the re- 
action seems terminated, the acid liquid is diluted, neutralized with chalk, 
and the filtered liquid mixed with acetate of lead. The insoluble saccharate 
of lead is washed, and decomposed by sulphuretted hydrogen The acid 
slowly crystallizes from a solution of syrupy consistence in long colourless 
needles : it has a sour taste, and forms soluble salts with lime and baryta. 
When mixed with nitrate of silver, it gives no precipitate, but, on the addi- 
tion of ammonia, a white insoluble substance separates, which is reduced, 
by gently warming the whole, to metallic silver, the vessel being lined with 
a smooth and brilliant coating of the metal. Nitric acid converts the sac- 
charic into oxalic acid. 

Xylotdin and pyroxylin. — When starch is mixed with nitric acid of spe- 
cific gravity 1-5, it is converted without disengagement of gas into a trans- 
parent, colourless jelly, which, when put into water, yields a white, curdy, 
insoluble substance: this is the 'new body xyloidin. When dry, it is white 
and tasteless, insoluble even in boiling water, but freely dissolved by dilute 
nitric acid, and the solution yields oxalic acid when boiled. Other sub- 
stances belonging to the same class also yield xyloidin ; paper dipped into 
the strongest nitric acid, quickly plunged into water, and afterwards dried, 
becomes in great part so changed ; it assumes the appearance of parchment, 
and acquires an extraordinary degree of combustibility. 

If pure finely divided ligneous matter, as cotton-wool, be steeped for a 
few minutes in a mixture of nitric acid of sp. gr. 1*5 and concentrated sul- 
phuric acid, squeezed, thoroughly washed and dried by very gentle heat, it 
will be found to have increased in weight- about 70 per cent., and to have be- 
come in the highest degree explosive, taking fire at a temperature not much 
above 300° (148° -8C), and burning without smoke or residue. This is 
pyroxylin, the gun-cotton of Professor Schoenbein. It differs from xyloidin 
in composition, in its mode of combustion, and in resisting the action of cer- 
tain liquids, as ether containing a little alcohol, which dissolve xyloidin with 
facility. To a solution of this description the name collodion has been given ; 
it is used in surgery. 

Both xyloidin and pyroxylin appear to the subsfitution-compounds, in 
which the elements of hyponitric acid replace respectively 3 and 5 equiva- 
lents of hydrogen in those of water in starch and lignin. The analytical 
results are not very uniform, but the formulae which best agree with them 
are, xyloidin C^H^NgCK^, and pyroxylin C^H^NgO^. 1 

An analogous compound is produced by the action of nitric acid upon 
mannite (vide p. 337). This substance may be crystallized from spirit, and 
contains C 6 H 4 N 3 18 ; it may be viewed as mannite, in which three equiva- 
lents of hydrogen are replaced by hyponitric acid. 

Mucic acld C ]2 H 8 14 ,2IIO. — Sugar of milk and gum, heated with nitric 
ncid somewhat diluted, furnish, in addition to a small quantity of oxalic acid, 

1 Pyroxylin obtained by the mixture of nitric and sulphuric acids, or by the action of a 
well cooled mixture of two parts of nitrate of potassa and three parts of concentrated sul- 
phuric acid, has the composition as given in the text, but is wholly insoluble in ether, or a 
mixture of ether and alcohol. 'When, however, the cotton-wool is steeped in the mixture of 
nitre and sulphuric acid at the temperature produced by their mixture, the resulting com- 
pound is readily soluble in ether and a mixture of ether and alcohol forming a transparent, 
viscid solution. Ammonia passed through this solution renders it quite fluid. The amino- 
niacal solution acted on by a large quantity of Mater yields a light white precipitate, inso- 
luble in water, while nitrate of ammonia remains in solution. The composition of the pre- 
cipitate is intermediate between xyloidin and pyroxylin. CaJIir.N-iOa.; four equivalents of 
hydrogen being replaced by four of hyponitric acid or four equivalents of the elements of 
water by four of nitric acid. It may be dried without alteration at the boiling temperature ; 
by heat it explodes with a slight residue of carbon. 
"The mixture of sulphuric and nitric acid forms from gum, glucose, and dextrine, explosive 
products wlr-h have not yet been fully examined. (Becbamp. Ann. Ch. et Phys. Feb. 

Mm >— it. b 



FERMENTATION OF SUGAR. 345 

a white nearly insoluble substance called mucic acid. It may be easily pre- 
pared by heating together in a flask or retort 1 part of milk-sugar, or gum. 
4 parts of nitric acid, and 1 of water ; the mucic acid is afterwards collected 
upon a filter, washed and dried. It has a slightly sour taste, reddens vege- 
table colours, and forms salts with bases. It requires for solution 66 parts 
of boiling water. Oil of vitriol dissolves it with red colour. Mucic acid is 
decomposed by heat, yielding, among other products, a volatile acid, the 
pyromucic, which is soluble in water, and crystallizes in a form resembling 
that of benzoic acid. Pyromucic acid is monobasic; it contains Ci H 5 O 5 ,HO. 

Suberic acid, C 16 H 12 6 ,2HO, is formed by the action of nitric acid on the 
peculiar ligneous matter of cork, and also on certain fatty bodies ; it much 
resembles mucic acid, but is more soluble in water. It is a bibasic acid. 
See farther on, Section VII., Oils and Fats. 

The following bodies are closely allied in. composition to oxalic acid : — 

Mellitic acid, C 4 3 ,HO. — This substance occurs, in combination with 
alumina, in a very rare mineral called mellite or lioney-stone, found in deposits 
of imperfect coal, or lignite. It is soluble in water and alcohol, and is crys- 
tallizable, forming colourless needles. It combines with bases : the melli- 
tates of the alkalis are soluble and crystallizable ; those of the earths and 
metals proper are mostly insoluble. 

Mellitate of ammonia yields by distillation two curious compounds, para- 
mide and euchronic acid. The former is a white, amorphous, insoluble sub- 
stance, containing C g IIN0 4 , (i.e., bimellitate of ammonia — 4 eq. of water), 
and convertible by boiling with water into bimellitate of ammonia. The 
latter forms colourless, sparingly soluble crystals containing in the anhy- 
drous state C l2 N0 6 ,2HO. In contact with metallic zinc and deoxidizing 
agents in general, euchronic acid yields a deep blue insoluble substance called 
euchrone. 

Rhodizonic and croconic acids. — When potassium is heated in a stream 
of dry carbonic oxide gas, the latter is absorbed in large quantity, and a 
black porous substance generated, which, when put into water, evolves in- 
flammable gas, and produces a deep red solution containing the potassa-salt 
of a peculiar acid; the rhodizonic: by adding alcohol to the liquid, the rho- 
dizonate of potassa is precipitated. This and the lead-salt are the only two 
compounds which have been fully examined ; the acid itself cannot be iso- 
lated. Rhodizonate of potassa is composed of C 7 7 3KO ; hence the acid 
would appear to be tribasic. 

When solution of rhodizonate of potassa is boiled, it becomes orange-yel- 
low from decomposition of the acid, and is then found to contain oxalate of 
potassa, free potassa, and a salt of an acid to which the term croconic in 
applied. This acid can be isolated ; it is yellow, easily crystallizable, and 
soluble both in water and alcohol. Crystallized croconic acid contains 
C 5 4 ,HO. 

THE FERMENTATION OP SUGAR, AND ITS PRODUCTS. 

The term fermentation is applied in chemistry to a peculiar metamorpho- 
sis of a complex organic substance, by a transportation of its elements under 
the agency of an external disturbing force, different from ordinary chemical 
attraction, and more resembling those obscure phenomena of contact already 
noticed, to which the expression katalysis is sometimes applied. The expla 
nation which Liebig has suggested of the cause and nature of the fermen- 
tative change is a very happy one, although of necessity only hypothetical 
It has long been known that one of the most indispensable conditions of that 
process is the presence in the fermenting liquid of certain azotized substan- 
ces, called ferments, whose decomposition proceeds simultaneously with thai 
of the body undergoing metamorphosis. They all belong to the clas* of al 



346 FERMENTATION OF SUGAR. 

Luminous principles, bodies which in a moist condition putrefy and decom- 
pose spontaneously. It is imagined that when these substances, in the act 
of undergoing change, are brought into contact with neutral ternary com- 
pounds of small stability, as sugar, the molecular disturbance of the body, 
already in a state of decomposition, may be, as it were, propagated to the 
other, and bring about destruction of the equilibrium of forces to which it 
owes its being. The complex body under these circumstances, breaks up 
into simpler products, which possess greater permanence. Whatever may 
be the ultimate fate of this ingenious hypothesis, it is certain that decom- 
posing azotized bodies not only do possess very energetic and extraordinary 
powers of exciting fermentation, but that the kind of fermentation set up is, 
in a great degree, dependent on the phase or stage of decomposition of the 
ferment. 

Alcohol; vinous fermentation. — A solution of pure sugar, in an open 
or close vessel, may be preserved unaltered for any length of time ; but, if 
putrescible azotized matters be present, in the proper state of decay, the 
sugar is converted into alcohol, with escape of carbonic acid. Putrid blood, 
white of egg, or flour-paste, will effect this ; by far the most potent alcoholic 
ferment is, however, to be found in the insoluble, yellowish, viscid matter 
deposited from beer in the act of fermentation, called yeast. If the sugar 
be dissolved in a large quantity of water, a due proportion of active yeast 
added, and the whole maintained at a temperature of 70° (21 -1C) or 80° 
(26° -6C), the change will go on with great rapidity. The gas disengaged 
will be found to be nearly pure carbonic acid ; it is easily collected and ex- 
amined, as the fermentation, once commenced, proceeds perfectly well in a 
close vessel, as a large bottle or flask, fitted with a cork and conducting- 
tube. When the effervescence is at an end, and the liquid has become clear, 
it will yield alcohol by distillation. Such is the origin of this important com- 
pound ; it is a product of the metamorphosis of sugar, under the influence 
of a ferment. 

The composition of alcohol is expressed by the formula C 4 H 6 2 : it is pro- 
duced by the breaking up of an equivalent of grape-sugar, C 24 H 28 28 , into 
4 eq.of alcohol, 8 of carbonic acid, and 4 of water. It is grape-sugar alons 
which yields alcohol, the ferment in the experiment above related first con- 
verting the cane-sugar into that substance. Milk-sugar may sometimes appa- 
rently be made to ferment, but a change into grape-sugar always really pre- 
cedes the production of alcohol. 

The spirit first obtained by distilling a fermented saccharine liquid is very 
weak, being diluted with a large quantity of water. By a second distilla- 
tion, in which the first portions of the distilled liquid are collected apart, it 
may be greatly strengthened ; the whole of the water cannot, however, be 
thus removed. The strongest rectified spirit of wine of commerce has a 
density of about 0-835, and yet contains 13 or 14 per cent, of water. Pure 
or absolute alcohol may be obtained from this by re-distilling it with half its 
weight of fresh quick-lime. The lime is reduced to coarse powder, and put 
into a retort ; the alcohol is added, and the whole mixed by agitation. The 
neck of the retort is securely stopped with a cork, and the mixture left for 
several days. The alcohol is distilled off by the heat of a water-bath. 

Pure alcohol is a colourless, limpid liquid, of pungent and agreeable taste 
and odour; its specific gravity at 60° (15°-5C) is 0-7938, and that of its 
vapour 1-613. It is very inflammable, burning with a pale bluish flame, free 
Irom smoke, and has never been frozen. Alcohol boils at 173° (78°-4C) when 
in the anhydrous condition ; in a diluted state the boiling-point is higher, 
being progressively raised by each addition of water. In the act of dilution 
a contraction of volume occurs, and the temperature of the mixture rise3 
many degrees , tVis takes place not only with pure alcohol, but with rectified 



ALCOHOL. 347 

spin*. It is miscible with water in all proportions, and, indeed, has a great 
attraction for the latter, absorbing its vapour from the air, and abstracting 
the moisture from membranes and other similar substances immersed in it. 
The solvent powers of alcohol are very extensive ; it dissolves a great num- 
ber of saline compounds, and likewise a considerable proportion of potassa. 
"With many of these substances it forms definite compounds. The substance 
which is produced by potassa, contains C 4 H 5 0,KO ; it may be likewise formed 
by acting with potassium upon anhydrous alcohol, when hydrogen is evolved. 
Alcohol dissolves, moreover, many organic substances, as the vegeto-alkalis, 
resins, essential oils, and various other bodies ; hence its great use in chemi- 
cal investigations and in several of the arts. 

The strength of commercial spirit is inferred from its density, when free 
from sugar and other substances added subsequent to distillation ; a table 
exhibiting the proportions of real alcohol and water in spirits of different 
densities will be found at the end of the volume. The excise proof spirit has 
a sp. gr, of 0-9198 at 60° (15° -5C), and contains 49^ per cent, by weight of 
real alcohol. 

Wine, beer, &c, owe their intoxicating properties to the alcohol they con- 
tain, the quantity of which varies very much. Port and sherry, and some 
other strong wines, contain, according to Mr. Brande, from 19 to 25 per cent, 
of alcohol, while in the lighter wines of France and Germany- it sometimes 
falls as low as 12 per cent. Strong ale contains about 10 per cent., ordinary 
spirits, as brandy, gin, whisky, 40 to 50 per cent., or occasionally more. 
These latter owe their characteristic flavours to certain essential oils, present 
in very small quantity, either generated in the act of fermentation or pur- 
posely added. 

In making wine, the expressed juice of the grape is simply set aside in 
large vats, where it undergoes spontaneously the necessary change. The 
vegetable albumin of the juice absorbs oxygen from the air, runs into decom- 
position, and in that state becomes a ferment to the sugar, which is gradu- 
ally converted into alcohol. If the sugar be in excess, and the azotized mat 
ter deficient, the resulting wine remains sweet ; but if, on the other hand„ 
the proportion of sugar be small, and that of albumin large, a dry wine is 
produced. When the fermentation stops, and the liquor becomes clear, it is 
drawn off from the lees, and transferred to casks, to ripen and improve. 

The colour of red wine is derived from the skins of the grapes, which in 
such cases are left in the fermenting liquid. Effervescent wines, as cham- 
pagne, are bottled before the fermentation is complete ; the carbonic acid is 
disengaged under pressure, and retained in solution in the liquid. The pro- 
cess requires much delicate management. 

During the fermentation of the grape-juice, or must, a crystalline, stony 
matter, called argol, is deposited. This consists chiefly of acid tartrate of 
potassa, with a little tartrate of lime and colouring matter, and is the 
source of all the tartaric acid met with in commerce. The salt in question 
exists in the juice in considerable quantity ; it is but sparingly soluble in 
water, but still less so in dilute alcohol ; hence, as the fermentation proceeds, 
and the quantity of spirit increases, it is slowly deposited. The acid of the 
juice is thus removed as the sugar disappears. It is this circumstance which 
renders grape-juice alone fit for making good wine: when that of gooseber- 
ries or currants is employed as a substitute, the malic and citric acids which 
these fruits contain cannot be thus withdrawn. There is, then, no other 
recourse but to add sugar in sufficient quantity to mask and conceal the 
natural acidity of the liquor. Such wines are necessarily acescent, prone to 
a second fermentation, an^, to many persons, at least, very unwholesome. 

Beer is a well-known liquor, of great antiquity, prepared from germinated 
grain, generally barley, and is used in countries where the vine does not 



348 ALCOHOL. 

flourish. The operation of malting is performed by steeping the "barley in 
water until the grains become swollen and soft, then piling it in a heap or 
couch, to favour the elevation of temperature caused by the absorption of 
ox}'gen from the air, and afterwards spreading it upon a floor, and turning 
it over from time to time, to prevent unequal heating. When germination 
has proceeded far enough, the vitality of the seed is destroyed by kiln-dry- 
ing. During this process, the curious substance already referred to, dias- 
tase, is produced, and a portion of the starch of the grain converted into 
sugar, and rendered soluble. 

In brewing, the crushed malt is infused in water at about 170° (76°. 6C), 
and the mixture left to stand during the space of two hours or more. The 
easily soluble diastase has thus an opportunity of acting upon the unaltered 
starch of the grain, and, changing it into dextrin and sugar. The clear 
liquor, or wort, strained from the exhausted malt, is then pumped in a cop- 
per boiler, and boiled with the requisite quantity of hops, for communicating 
a pleasant bitter flavour, and conferring on the beer the property of keep- 
ing without injury. The flowers of the hop contain a bitter, resinous prin- 
ciple, called lupulin, and an essential, oil, both of which are useful. 

When the wort has been sufficiently boiled, it is drawn from the copper, 
and cooled, as rapidly as possible, to near the ordinary temperature of the 
air, in order to avoid an irregular acid fermentation, to which it would oth- 
erwise be liable. It is then transferred to the fermenting vessels, which in 
large breweries are of great capacity, and mixed with a quantity of yeast, 
the product of a preceding operation, by which the change is speedily in- 
duced. This is the most critical part of the whole operation, and one in 
which the skill and judgment of the brewer are most called into play. The 
process is in some measure under control by attention to the temperature of 
the liquid, and the extent to which the change has been carried is easily 
known by the diminished density, or attenuation, of the wort. The fermenta- 
tion is never suffered to run its full course, but is always stopped at a par- 
ticular point, by separating the yeast, and drawing off the beer into casks. 
A slow and almost insensible fermentation succeeds, which in time renders 
the beer stronger and less sweet than when new, and charges it with carbonic 
acid. 

Highly coloured beer is made by adding to the malt a small quantity of 
strongly dried or charred malt, the sugar of which has been changed to cara- 
mel ; porter and stout are so prepared. 

The yeast of beer is a very remarkable substance, and has excited much 
attention. To the naked eye it is a greyish-yellow soft solid, nearly insoluble 
in water, and dries up to a pale brownish mass, which readily putrefies when 
moistened, and becomes offensive. Under the microscope it exhibits a kind 
of organized appearance, being made up of little transparent globules, which 
sometimes cohere in clusters or strings, like some of the lowest members of 
the vegetable kingdom. Whatever may be the real nature of the substance, 
no doubt can exist that it is formed from the soluble azotized portion of the 
grain during the fermentive process. No yeast is ever produced in liquids 
free from azotized matter; that added for the purpose of exciting fermenta- 
tion in pure sugar is destroyed, and rendered iuert thereby. When yeast is 
deprived, by straining and strong pressure, of as much water as possible, it 
may be kept in a cool place, with unaltered properties, for a long time ; oth- 
erwise, it speedily spoils. 

The dxStiller, who prepares spirits from grain, makes his wort, or wash, 
much in the same manner as the brewer; he uses, however, with the malt a 
large quantity of raw grain, the starch of which suffers conversion into sugar 
by the diastase of the malt, which is sufficient for his purpose. He does not 
boil his mfusion with hops, but proceeds at once to the fermentation, which 



LACTIC ACID. 349 

he pushes as far as possible by large and repeated doses of yeast. Alcohol 
is manufactured in many cases from potatoes ; the potatoes are ground to 
pulp, mixed with hot water and a little malt, to furnish diastase, made to 
ferment, and then the fluid portion distilled. The potato-spirit is contami- 
nated by a very offensive volatile oil, again to be mentioned ; the crude pro- 
duct from corn contains a substance of a similar kind. The business of the 
rectifier consists in removing or modifying these volatile oils, and in replacing 
them by others of a more agreeable character. 

In making bread, the vinous fermentation plays an important part ; th 
yeast added to the dough converts the small portion of sugar the meal natu 
rally contains into alcohol and carbonic acid. The gas thus disengaged 
forces the tough and adhesive materials into bubbles, which are still farther 
expanded by the heat of the oven, which at the same time dissipates the 
alcohol ; hence the light and spongy texture of all good^ bread. Sometimes 
carbonate of ammonia is employed with the same view, being completely 
volatilized by the high temperature of the oven. Bread is now sometimes 
made by mixing a little hydrochloric and carbonate of soda in the dough ; if 
proper proportions be taken, and the whole throughly mixed, the operation 
appears to be very successful. The use of leaven is one of great antiquity ; 
this is merely dough in a state of incipient putrefaction. When mixed with 
a large quantity of fresh dough, it excites in the latter the alcoholic fermenta- 
tion, in the same manner as yeast, but less perfectly ; it is apt to communicate 
a disagreeable sour taste and odour. 

Lactic acid ; lactic acid fermentation ; butyric acid ferbientatiost. 
• — Azotized albuminous substances, which in an advanced state of putrefactive 
.change act as alcohol-ferments, often possess, at certain periods of decay, the 
property of inducing an acid /fermentation in sugar, the consequence of which 
is the conversion of that substance into lactic acid. Thus, the azotized matter 
of malt, when suffered to putrefy in water for a few days, acquires the power 
of acidifying the sugar which accompanies it, while in a more advanced state 
of decomposition it converts, under similar circumstances, the sugar into 
alcohol. The glutin of grain behaves in the same manner: wheat flour, made 
into a paste with water, and left four or five days in a warm situation, be- 
comes a true lactic acid ferment; if left a day or two longer, it changes its 
character, and then acts like common yeast. Moist animal membranes, in a 
slightly decaying condition, often act energetically in developing lactic acid. 
Cane-sugar, probably by previously becoming grape-sugar, and the sugar 
of milk, both yield lactic acid, the latter, however, most readily, the grape- 
sugar having a strong tendency towards the alcoholic change. A good method 
of preparing lactic acid is the following. An additional quantity of milk- 
sugar is dissolved in ordinary milk, which is then set aside in a warm place, 
until it becomes sour and coagulated. The casein of the milk absorbs oxygen 
from the air, runs into putrefaction, and acidifies a portion of the sugar. 
The lactic acid formed, after a time coagulates and renders insoluble the 
casein, and the production of that acid ceases. By carefully neutralizing, 
however, the free acid by carbonate of soda, the casein becomes soluble, 
and, resuming its activity, changes a fresh quantity of sugar into lactic acid, 
which may be also neutralized, and by a sufficient number of repetitions of 
this process all the sugar of milk present may, in time, be acidified. When 
this has taken place, the liquid is boiled, filtered, and evaporated to dryness 
in a water-bath. The residue is treated with hot alcohol, which dissolves out 
the lactate of soda. The alcoholic solution may then be decomposed by the 
cautious addition of sulphuric acid, which precipitates sulphate ff soda, inso- 
luble in spirit. The free acid may, if needful, be neutralized with lime, and 
the resulting salt purified by re-crystallization and the use of animal char- 
coal, after which it may be decomposed by oxalic acid 
30 



350 LACTIC ACID. 

The following process will be found more economical on a large scale : — 
A mixture is made of two gallons of milk, which may be stale or skimmed 
milk, six pounds of raw sugar, twelve pints of water, eight ounces of putrid 
cheese, and four pounds of chalk, which should be mixed up to a creamy 
consistence with some of the liquid. This mixture is exposed in a loosely- 
covered jar to a temperature of about 86° (30°C), with occasional stirring. 
At the end of two or three weeks it will be found converted into a semi-solid 
mass or pudding of lactate of lime, which may be drained, pressed, and 
purified by re-crystallization from water. 

The lactate of lime may be decomposed by the necessary quantity of pure 
oxalic acid, the filtered liquor neutralized with carbonate of zinc, and, after 
a second filtration, evaporated until the zinc-salt crystallizes out on cooling. 
The latter may, lastly, be re-dissolved in water, and decomposed by sul- 
phuretted hydrogen, in order to obtain the free acid. 

If in the first part of the process the solid lactate of lime be not removed 
at the proper period from the fermenting liquid, it will gradually re-dissclve 
and disappear. On examination the liquid will then be found to consist 
chiefly of a solution of butyrate of lime. 

This second stage of the process, to which the name of butyric acidfer • 
mentation has been given, is attended with an evolution of hydrogen and 
carbonic acid. It will be mentioned more in detail in the Section on Oils 
and Fats. 

Lactic acid may be extracted from a great variety of liquids containing 
decomposing organic matter, as sauerkraut, a preparation of white cabbage; 
the sour liquor of the starch-maker, &c. It has been supposed to exist in 
the blood, urine, and other animal fluids ; recent researches have, however, 
failed to detect it in either blood or urine, although it has been shown by 
Liebig to exist in considerable quantity in the juice of flesh or muscle. 

Lactic acid has been lately produced artificially in a most remarkable 
manner by the action of nitrous acid upon alanine. (See the Section on 
Organic Bases.) 

Solution of lactic acid may be concentrated in the vacuum of the air- 
pump, over a surface of oil of vitriol, until it acquires the aspect of a colour- 
less, syrupy liquid, of sp. gr. 1-215. It has an intensely sour taste and 
acid reaction ; it is hygroscopic, and very soluble in water, alcohol, and 
ether. It forms soluble salts with all the metallic oxides. The syrupy acid 
contains C 6 H 5 5 -|-HO, or C 12 H 10 O ]0 -f-2HO, the water being basic, and 
susceptible of replacement by a metallic oxide. 

When syrupy lactic acid is heated in a retort to 266° (130°C), water con- 
taining a little actic acid distils over, and the residue on cooling forms a yel- 
lowish solid fusible mass, very bitter, and nearly insoluble in water. This is 
anhydrous lactic acid, C 6 H 5 5 . Long-continued boiling with water converts 
it into ordinary lactic acid. When this substance is farther heated it decom- 
poses, yielding numerous products. One of these is laciide, formerly errone- 
ously called anhydrous lactic acid, a volatile substance, crystallizing in 
brilliant colourless rhombic plates, which, when put into water, slowly dis- 
solve, with production of common lactic acid. Lactide contains C 6 H 4 4 ; it 
combines with ammonia, forming lactamide, C 6 H 7 N0 4 , a colourless, crystalli- 
zable, soluble substance, resembling in its chemical relations oxamide. 
Another product of the action of heat on lactic acid is lactone, a colourless 
volatile liquid, boiling at 198° (92° -2C.) Acetone is also formed, and carbonic 
oxide and carbonic acid are disengaged. 

A salt of lactic acid, gently heated with five or six parts of oil of vitriol, 
yields an enormous quantity of perfectly pure carbonic oxide gas. 

The most important and characteristic of the lactates are those of lime and 
the oxide of zinc. 



ETHER. 351 

Lactate of lime, CaO,C 6 H 5 5 -j-5IIO, exists ready-formed, to a small ex- 
tent, in Nux vomica. When pure, it crystallizes in tufts of minute white 
needles grouped in concentric layers. It dissolves in 10 parts of cold, and 
indefinitely in boiling water, melting in its water of crystallization at that 
temperature. 

Lactate of zixc, ZnO,C 6 H 5 5 -f-3IIO, is deposited from a hot solution in 
small brilliant 4-sided prismatic crystals, which require for solution 58 parts 
of cold and 6 of boiling water. 

Lactate of protoxide of ieox, FeO,C 6 H 5 5 -j-3HO, is now used in medi- 
cine. It is prepared by adding alcohol to a mixture of lactate of ammonia 
and protochloride of iron, when the salt is precipitated in the form of small 
yellowish needles. 

When the expressed juice of the beet is exposed to a temperature of 90° 
(32°-9C) or 100° (37°*7C) for a considerable time, the sugar it contain? 
suffers a peculiar kind of fermentation, to which the term viscous has been 
applied. Gases are evolved which contain hydrogen, and when the change 
appears complete, and the products come to be examined, the sugar is found 
to have disappeared. Mere traces of alcohol are produced, but, in place of 
that substance, a quantity of lactic acid, mannite, and a mucilaginous sub- 
stance resembling gum- Arabic, and said to be identical with gum in com- 
position. 

Pure sugar can be converted into this substance ; by boiling yeast or the 
glutin of wheat in water, dissolving sugar in the filtered solution, and ex- 
posing it to a tolerably high temperature, the viscous fermentation is set up, 
and a large quantity of the gummy principle generated. A little gas is at 
the same time disengaged, which is a mixture of carbonic acid and hydrogen. 



products of the action of acids on alcohol. 

Ether; oxide of ethyl. — When equal weights of rectified spirit and oil 
of vitriol are mixed in a retort, the latter connected with a good condensing 
arrangement, and the liquid heated to ebullition, a colourless and highly vo- 
latile liquid, long known under the name of ether, or sulphuric ether, distils 
over. The process must be stopped as soon as the contents of the retort 
blacken and froth, otherwise the product will be contaminated with other 
substances, which then make their appearance. The ether obtained may be 
mixed with a little caustic potassa, and re-distilled by a very gentle heat. 

Pure ether is a colourless, transparent, fragrant liquid, very thin and mo- 
bile. Its sp. gr. at 60° (15°-5C) is about 0-720; it boils at 96° (35°-5C) 
under the pressure of the atmosphere, and bears without freezing the se- 
verest cold. When dropped on the hand it occasions a sharp sensation of 
cold, from its rapid volatilization. Ether is very combustible ; it burns with 
a white flame, generating water and carbonic acid. Although the substance 
itself is one of the lightest of liquids, its vapour is very heavy, having a 
density of 2-586. Mixed with oxygen gas, and fired by the electric spark, 
or otherwise, it explodes with the utmost violence. Preserved in an imper- 
fectly-stopped vessel, ether absorbs oxygen, and becomes acid from the pro- 
duction of acetic acid ; this attraction for oxygen is increased by elevation 
of temperature. It is decomposed by transmission through a red-hot tube 
into defiant gas, light carbonetted hydrogen, and a substance yet to be de- 
scribed, aldehyde. 



352 COMPOUND ETHERS. 

Ether is miscible -with alcohol in all proportions, but not with water ; it 
dissolves to a small extent in that liquid, 10 parts of water taking up 1 part, 
or thereabouts, of ether. It may be separated from alcohol, provided the 
quantity of the latter be not excessive, by an addition of water, and in this 
manner samples of commercial ether maybe conveniently examined. Ether 
is a solvent for oily and fatty substances generally, and phosphorus to a 
small extent, a few saline compounds and some organic principles, but its 
powers in this respect are much more limited than those of alcohol or water. 

Ether was the first part of a great number of analogous substances in 
which the property of producing temporary insensibility to pain was recog- 
nized. In surgical operations, the use of ether is now superseded by that 
of chloroform. 

Ether is found by analysis to contain C 4 H 5 0; it, therefore, differs from al- 
cohol, C 4 H 6 2 , by the elements of water. Alcohol is often regarded as the 
hydrate of ether; but as ether cannot be made to combine with water di- 
rectly, and as alcohol cannot be converted into ether by the abstraction of 
water by the aid of substances known to possess a high affinity for that body, 
such a view was always looked upon as hypothetical. Recent experiments 
have, in fact, shown that a very different relation exists between alcohol and 
ether. We shall return to these researches, when we consider the theory of 
the production of ether, which will be discussed partly in connection with 
the history of sulphovinic acid, and partly with that of the methyl-com- 
pounds. 

Compound ethers ; ethyl-theory ; ethyl. — The so-called compound 
ethers constitute a very large and important class of substances derived 
from alcohol, and containing either the elements of ether, in combination 
with those of an oxygen-acid, inorganic or organic, or the elements of ole- 
fiant gas in union with those of a hydrogen-acid. The relations of these 
compounds to alcohol and the acids are most simply and clearly illustrated 
by comparing them with ordinary salts, in which the metal is replaced by a 
salt-basyle termed ethyl, containing C 4 H 5 . This substance forms haloid-salts 
by combining with chlorine, iodine, bromine, &c, and its oxide, identical or 
isomeric with common ether, with oxygen-acids, like basic metallic oxides in 
general. A body containing carbon and hydrogen in the proportions indi- 
cated by the formula C 4 H 5 , has been lately obtained by Dr. Frankland, from 
one of the members of this group of compounds, and describe -7 under the 
name of ethyl. It is formed by exposing iodide of ethyl in sealed tubes, to 
the action of metallic zinc, at a temperature of 320° (160°C). 1 In this re- 
action, the iodine of the iodide of ethyl C 4 H 5 I combines with the zinc, and 
ethyl is set free. On opening the sealed tubes, and allowing the gas, which 
is ethyl mixed with several secondary products (especially defiant gas), to 
pass into a freezing mixture, the temperature of which is kept below — 9° 
( — 23°C), the ethyl condenses to a colourless mobile liquid. It is not at- 
tacked by concentrated sulphuric and nitric acids. Chlorine acts upon it 
under the influence of light, but not in the dark. Hitherto no compound 
ether has been reproduced from ethyl. The ethyl-theory, proposed by the 
sagacity of Liebig long before the separation of ethyl itself, will be found 
highly useful as an aid to the memory ; it must not, however, be forgotten 
that the compound ethers are distinguished by important characters from 
real and undoubted salts. 

Table of EihyhCompounds. 

Ethyl, symbol Ae C 4 H 5 

Oxide of ethyl; ether C 4 H 6 

Hydrate of the oxide; alcohol C 4 H 5 0,HO 

x See also, zinc-ethyl, page 3C8. 



COMPOUND ETHERS. 353 

Chloride of ethyl C 4 H 5 C1 

Bromide of ethyl C 4 H 5 Br 

Iodide of ethyl C 4 H 5 I 

Cyanide of ethyl C 4 H 5 Cy 

Nitrate of oxide of ethyl C 4 H 5 0,N0 5 

Nitrite of oxide of ethyl C 4 H 5 0,N0 3 

Oxalate of oxide of ethyl C 4 H 5 0,C 2 3 

Hydride of ethyl C 4 H 5 fi 

Zinc-ethyl C 4 H 5 Zn 

&c. &c. 

The ethers of many of the acids may he formed by the direct action of 
these latter upon alcohol at a high temperature, the elements of water being 
displaced by those of the acid; this is chiefly conspicuous "with the volatile 
acids. A more ready general method of forming them, .however, is to distil 
a mixture of alcohol, sulphuric acid, and a salt of the acid the ether of which 
is required. The fatty acids, which in general cannot be distilled without 
more or less decomposition, yield their ethers with great facility by the action 
of hydrochloric acid gas upon an alcoholic solution of the acid. 

The compound ethers are mostly volatile aromatic liquids, in a few cases 
crystallizable solids, without action on vegetable colours, sparingly soluble 
in water, but dissolved in all proportions by alcohol and ether. They are 
not acted upon in the cold by alkaline carbonates, but suffer decomposition 
with more or less difficulty when heated with aqueous solutions of caustic 
alkali, a salt of the acid of the ether being usually generated, and alcohol 
formed and set free. An alcoholic solution of hydrate of potassa or soda is 
more active in this respect. The same kind of decomposition is often 
brought about by the prolonged contact of boiling water. 

Chloride of ethyl; light hydrochloric ether; AeCl. — Rectified 
spirit of wine is saturated with dry hydrochloric acid gas, and the product 
distilled with very gentle heat; or a mixture of 3 parts oil of vitriol and 2 
of alcohol is poured upon 4 parts of dry common salt in a retort, and heat 
applied ; in either case the vapour of the hydrochloric ether should be con- 
ducted through a little tepid water in a wash-bottle, and then conveyed .'.nto 
a small receiver surrounded by ice and salt. It is purified from adhering 
water by contact with a few fragments of fused chloride of calcium. Hy- 
drochloric ether is a thin, colourless, and excessively volatile liquid, of a 
penetrating, aromatic, and somewhat alliaceous odour. At the freezing point 
of water, its sp. gr. is 0-921, and it boils at 50° (12°-5C) ; it is soluble in 10 
parts of water, is not decomposed by solution of nitrate of silver, but is 
quickly resolved into chloride of potassium and alcohol by a hot solution of 
caustic potassa. 

Bromide of ethyl; hydeobromic ether; AeBr. — This is prepared by 
distilling a mixture of 8 parts bromine, 1 part phosphorus, and 32 parts 
alcohol. The phosphorus is converted into phosphorous acid by the oxygen 
of the alcohol, when the ethyl combines with the bromine ; 3 equivalents of 
alcohol, 3 equivalents of bromine, and 1 equivalent of phosphorus, yield 3 
equivalents of bromide of ethyl, 3 equivalents of water, and 1 equivalent of 
phophorous acid. It is a very volatile liquid, boiling at 106° (41°C), of 
penetrating taste and smell, and superior in density to water. 

Iodide of ethyl ; hydriodic ether ; Ael. — Obtained by gradually mix- 
ing, with precaution, 1 part of phosphorus, 5 parts of alcohol, and 10 parts 
of iodine (1 eq. of phosphorus, 3 eq. of alcohol, and 3 eq. of iodine), and 
distilling. The reaction is analagous to that described in the case of the 
bromide. Iodide of ethyl is a colourless liquid, of penetrating and ethereal 
odour, having a density of 1-92, and boiling at 158° (70°C). It becomes red 
30* 



354 COMPOUND ETHERS. 

by contact with air from a commencement of decomposition. This substance 
has become highly important as a source of ethyl, and from its remarkable 
deportment with ammonia, which will be discussed in the Section on Organic 
Bases. 

Sulphide of ethyl ; AeS. — Formed by the action of chloride of ethyl 
upon a solution of the protosulphate of potassium. It is colourless, has a 
disagreeable garlic odour, and boils at 180° (82°C). 

Cyanide of ethyl, AeCy. — This is produced when a mixture of sulphovi- 
nate of potassa and cyanide of potassium, both in a dry state, is slowly 
heated. It is colourless, when perfectly pure it has a powerful, not disa- 
greeable odour, and a sp. gr. of 0-788. It boils at 190°-4 (88°C). This 
substance has lately been studied by Drs. Kolbe and Frankland. They have 
found that cyanide of ethyl differs from the ordinary ethers in its deportment 
with the alkalis. Instead of yielding cyanide of potassium and alcohol, it is 
converted into ammonia and propionic acid, C 5 II 5 3 ,HO, a peculiar acid 
closely allied to acetic acid, and which will be noticed more in detail under 
the head of acetone. Cyanide of ethyl, in this reaction, absorbs 4 equiva- 
lents of water : — ■ 

1 eq. of cyanide of ethyl.... C 6 IT 5 N I 1 eq. of propionic acid C 6 II 6 4 

4 eq. of water .... II 4 4 | 1 eq. of ammonia H 3 N 

C«H 9 N0 4 I CeHgNQJ 

(See cyanide of methyl.) — When acted upon by potassium, cyanide of ethyl 
furnishes a gas, the nature of which is not definitely settled ; the residue 
contains cyanide of potassium and an organic alkali cyanethine, which con- 
tains C, S H 15 N 3 , and is formed by the coalescence of three equivalents of the 
cyanide. 

Sulphite of oxide of ethyl ; sulphurous ether ; AeO,S0 2 . — This sub- 
stance was obtained by adding absolute alcohol in excess to subchloride of 
sulphur. Hydrochloric acid is evolved, and sulphur deposited, while the 
sulphite of ethyl distils as a limpid strongly smelling liquid, of sp. gr. 1-085, 
boiling at 338° (170°C), it is slowly decomposed by water. 

Sulphate of oxide of ethyl; sulphuric ether; AeO,S0 3 . — This sub- 
stance has been only recently obtained. It is formed by passing the vapour 
of anhydrous sulphuric acid into perfectly anhydrous ether. A syrupy liquid 
is produced, which is shaken with 4 vols, of water and 1 vol. of ether, when 
two layers are formed; the lower contains sulphovinic acid, and various other 
compounds, while the upper layer consists of an ethereal solution of sul- 
phate of ethyl. At a gentle heat the ether is volatilized, and the sulphate 
of ethyl remains as a colourless liquid. It cannot be distilled without decom- 
position. 

Phosphate of oxide of ethyl ; phosphoric ether. — See phosphovinic 
acid. 

Nitrate of oxide of ethyl; nitric ether; AeO.N0 3 . — The nitrate 
likewise has only recently been obtained ; it is prepared by cautiously dis- 
tilling a mixture of equal weights of alcohol and moderately strong nitric 
acid, to which a small quantity of nitrate of urea has been added. The ac- 
tion of nitric acid upon alcohol is peculiar; the facility with which that acid 
is deoxidized by combustible bodies, leads, under ordinary circumstances, to 
the production of nitrous acid on the one baud, and an oxidized product of 
alcohol on the other, a nitrite of the oxide of ethyl being generated instead 
of a nitrate. M. Millon has shown that the addition of urea, from reasons 
to be explained when this compound will be described, entirely prevents the 
formation of that substance, and at the same time preserves the alcohol from 
oxidation by undergoing that change in its place, the sole liquid product 



COMPOUND ETHERS. 855 

being the new ether. The experiment is most safely conducted on a small 
scale, and the distillation must be stopped when seven-eighths of the whole 
have passed over ; a little water added to the distilled product separates the 
nitric ether. Nitric ether has a density of 1-112; it is insoluble in water, 
has an agreeable sweet taste and odour ; and is not decomposed by an aque- 
ous solution of caustic potassa, although that substance dissolved in alcohol 
attacks it even in the cold, with production of nitrate of potassa. Its vapour 
is apt to explode when strongly heated. 

Nitrite or oxide of ethyl ; nitrous ether ; AeO,N0 3 . — Pure nitrous 
ether can only be obtained by the direct action of the acid itself upon alcohol. 
1 part of potato-starch, and 10 parts of nitric acid, are gently heated in 
a capacious retort or flask, and the vapour of nitrous acid thereby evolved 
conducted into alcohol mixed with half its weight of water, contained in a 
two-necked bottle, which is to be plunged into cold water, and connected with 
a good condensing arrangement. All elevation of temperature must be care- 
fully avoided. The product of this operation is a pale yellow volatile liquid, 
possessing an exceedingly agreeable odour of apples ; it boils at 62° (16°-6C), 
and has a density of 0-947. It is decomposed by potassa, without darkening, 
into the nitrite of the base, and alcohol. 

Nitrous ether, but contaminated with aldehyde, may be prepared by the 
following simple method: — Into a tall cylindrical bottle or jar are to be 
introduced successively 9 parts of alcohol of sp. gr. 0-830, 4 parts of water, 
and 8 parts of strong fuming nitric acid ; the two latter are added by means 
of a long funnel with very narrow orifice, reaching to the bottom of the bottle, 
so that the contents may form three distinct strata, which slowly mix 
from the solution of the liquids in each other. The bottle is then loosely 
stopped, and left two or three days in a cool place, after which it is found to 
contain two laj'ers of liquids, of which the uppermost is the ether. It is puri- 
fied by rectification. A somewhat similar product may be obtained by care- 
fully distilling a mixture of 3 parts rectified spirit and 2 of nitric acid of 1-28 
sp. gr. ; the fire must be withdrawn as soon as the liquid boils. 

The sweet spirits of nitre of pharmacy, prepared by distilling three pounds 
of alcohol with four ounces of nitric acid, is a solution of nitrous ether, alde- 
hyde, and perhaps other substances, in spirit of wine. 

Carbonate of oxide of ethtl ; carbonic ether; AeO,C0 2 . — Fragments 
of potassium or sodium are dropped into oxalic ether as long as gas is disen- 
gaged ; the brown pasty product is then mixed with water and distilled. The 
carbonic ether is found floating upon the surface of the water of the receiver 
as a colourless, limpid liquid of aromatic odour and burning taste. It boils 
at 259° (126°C), and is decomposed by an alcoholic solution of potassa into 
carbonate of that base and alcohol. The reaction which gives rise to this 
substance is unexplained. 

Silicic and boracic ethers. — A N number of these compounds appear to 
exist, containing different proportions of the acids. Silicic ether, containing 
3AeO,Si0 3 , was obtained by M. Ebelmen by the action of anhydrous alcohol 
upon chloride of silicium. It is a colourless, limpid, aromatic liquid, of sp. 
gr. 0-933, boiling at 329° (165°C), and decomposed by water with production 
of silicic acid and alcohol. In contact with moist air it is gradually resolved 
into translucent hydrate of silica, which becomes in the end hard enough to 
scratch glass. By substituting ordinary spirit for absolute alcohol, other 
compounds containing a larger portion of silicic acid are obtained. 

Boracic ether was procured by a similar process, substituting the chloride 
of boron for chloride of silicium. It formed a thin, limpid liquid of agreeable 
odour, having the sp. gr. of 0-885, and boiling at 246° (118°C). It is decom- 
posed by water. Its alcoholic solution burns with a fine green flame, throw 
ing off a thick smoke of boracic acid. It contains 3AeO,Bo0 3 . A second 



356 COMPOUND ETHERS. 

boi\acic ether in the form of a solid glassy fusible substance, containing 
AeO,2BoG 3 , was formed by the action of fused boracic acid upon aJbsolute 
alcohol. It is volatile in the vapour of alcohol only, and is decomposed by 
water. 

Of the ethers of the organic acids, the following are the most important: — 

Oxalate of the oxide of ethyl; oxalic ether; AeO,C 2 3 . — This com- 
pound is most easily obtained by distilling together 4 parts binoxalate of 
potassa, 5 parts oil of vitriol, and 4 parts strong alcohol. The distillation 
may be pushed nearly to dryness, and the receiver kept warm to dissipate 
any ordinary ether that may be formed. The product is mixed with water, 
by which the oxalic ether is separated from the undecomposed spirit ; it is 
repeatedly washed to remove adhering acid, and re-distilled in a small retort, 
the first portions being received apart and rejected. Another .very simple 
process consists in digesting equal parts of alcohol and dehydrated oxalic 
acid, in a flask furnished with a long glass tube, in which the volatilized spirit 
may condense. After 6 or 8 hours' digestion, the mixture generally contains 
only traces of oxalic acid which is not etherified. 

Pure oxalic ether is a colourless, oily liquid, of pleasant aromatic odour, 
and 1-09 sp. gr. It boils at 363° (183°-8C) is but little soluble in water, 
and is readily decomposed by caustic alkalis into an oxalate and alcohol. 
With solution of ammonia in excess, it yields oxamide and alcohol. C 4 H 5 0, 
C 2 3 -f NH 3= C 2 2 ,NH 2 -fC 4 H 5 0,HO. This is the best process for preparing 
oxamide, which is obtained perfectly white and pure. (See page 343.) When 
dry gaseous ammonia is conducted into a vessel containing oxalic ether, the 
gas is rapidly absorbed, and a white solid substance produced, which is so- 
luble in hot alcohol, and separates, on cooling, in colourless, transparent, 
scaly crystals. They dissolve in water, and are both fusible and volatile. 
The name oxamethane is given to this body ; it consists of C 8 H 7 N0 6 =C 4 H 5 0, 
C 4 H 2 N0 5 , i. e., the ether of oxamic acid (see page 343). The same substance 
is formed when ammonia in small quantity is added to a solution of oxalic 
ether in alcohol. 

When oxalic ether is treated with dry chlorine in excess in the sunshine, 
a white, colourless, crystalline, fusible body is produced, insoluble in water 
and instantly decomposed by alcohol. It contains C 6 C1 5 4 , or oxalic ether 
in which the whole of the hydrogen is replaced by chlorine. 

Acetate of oxide of ethyl; acetic ether; Ae0,C 4 H 3 3 . — Acetic ether 
is conveniently made by heating together in a retort 3 parts of acetate of 
potassa, 3 parts of strong alcohol, and 2 of oil of vitriol. The distilled pro- 
duct is mixed with water, to separate the alcohol, digested first with a little 
chalk, and afterwards with fused chloride of calcium, and, lastly, rectified. 
The pure ether is an exceedingly fragrant, limpid liquid ; it has a density of 
0-890, and boils at 165° (73°-8C). Alkalis decompose it in the usual manner. 
When treated with ammonia, it yields acetamide, a crystalline substance 
soluble in water and alcohol, which contains C 4 H 5 NO 2 =:0 4 H 3 O 2 .NH 2 , i. e., 
acetate of ammonia — 2 equivalents of water. Its formation is analogous to 
that of oxamide. Alkalis and acids reconvert it into ammonia and acetic 
acid. When treated with nitrous acid, it vields acetic acid, water and ni- 
trogen gas, C 4 H 5 N0 2 +N0 3 =C 4 H 3 3 ,HO-f HO-f 2N. 

Formate of the oxide of ethyl ; formic ether; AeO,C 2 H0 3 . — A mix- 
ture of 7 parts of dry formate of soda, 10 of oil of vitriol, and 6 of strong 
alcohol, is to be subjected to distillation. The formic ether, separated by 
the addition of water to the distilled product, is agitated with a little mag- 
nesia, and left several days in contact with chloride of calcium. Formic 
eiher is colourless, has an aromatic smell, and density of 915, and boils at 
133° (5G'"C). Watei dissolves til's substance to a small extent. 



COMPOUND ETHERS. 357 

The ethers of many of the vegetable acids have been obtained and de- 
scribed. 

The ethers of cyanic and cyanuric acids have been formed and studied. 
The desci'iption of these remarkable substances and of their important pro- 
ducts of decomposition is postponed until the history of the acids themselves 
has been given. 

Ethers of the fatty acids. — Normal stearic ether has not yet been ob- 
tained. By passing hydrochloric acid gas into an alcoholic solution of stearic 
acid, Redtenbacher succeeded in obtaining the compound AeO,HO,C 68 H 66 5 . 
It resembled white wax, was inodorous and tasteless, melted at 8G° (30°C), 
and could not be distilled without decomposition. It was readily decomposed 
by boiling with caustic alkalis. Margaric ether is prepared by a similar mode 
of proceeding. When purified from excess of acid by agitation with succes- 
sive small quantities of weak spirit, and afterwards made to crystallize 
slowly from the same menstruum, it forms regular, brilliant, colourless crys- 
tals, fusible at 70° (21°-1C), and distilling without decomposition ; when less 
pure it is in great part destroyed by this latter process. Margaric ether 
contains AeOjC^AggOg. An oleic ether, and corresponding compounds of seve- 
ral other less important fatty acids, have been formed and described. They 
greatly resemble each other in characters. 

Butyric and valerianic ethers, AeO,C 8 H 7 3 , and AeO,C 10 H 9 O 3 . — The 
ether-compounds of these acids are easily obtained by the preceding process. 
They are fragrant volatile liquids, having an odour resembling that of the 
rind of the pine-apple. They are used for flavouring brandy. They are 
lighter than water, boil at a high temperature, and possess the constitution 
and general character of the class of bodies to which they belong. 

(Enanthic ether. — The aroma possessed by certain wines appears due to 
the presence of the ether of a peculiar acid called oznanthic, and which is pro- 
bably generated during fermentation. When such wines are distilled on the 
large scale, an oily liquid passes over towards the close of the operation, 
which consists, in great measure, of the crude ether ; it may be purified by 
agitation with solution of carbonate of potassa, freed from water by a few 
fragments of chloride of calcium, and re-distilled. (Enanthic ether is a thin, 
colourless liquid, having a powerful and almost intoxicating vinous odour ; 
it has a density of 0-862, boils at 482° (250°C), and is but sparingly soluble 
in water, although, like the compound ethers in general, it dissolves with 
facility in alcohol. It contains C 22 H ]2 4 , or AeO,C 18 H ]7 3 . 

A hot solution of caustic potassa instantly decomposes cenanthic ether ; 
alcohol distils over, and oenanthate of potassa remains in the retort; the 
latter is readily decomposed by warm dilute sulphuric acid, with liberation of 
cenanthic acid. Purified by repeated washing with hot water, cenanthic acid 
presents the appearance of a colourless, inodorous oil, which at 77° (25°C) 
becomes a soft solid, like butter. It reddens litmus paper, and dissolves 
easily in solutions of the alkaline carbonates and in spirit, and very much 
resembles the fatty acids, to be hereafter described, the products of saponi- 
fication. The acid thus obtained is a hydrate, composed of Ci 8 H 17 3 -f-HO. 
An acid of exactly the same composition has been obtained from Pelargonium 
roseum, and described by the name of pelargonic acid. It is likewise pro- 
duced, together with a host of similar acids, by the action of nitric acid upon 
oleic acid. (Enanthic ether may be reproduced by distilling a mixture of 5 
parts sulphovinate of potassa, and 1 part hydrated cenanthic acid, or perhaps 
better, by the ordinary process for the ethers of the fatty acids. 

Culorocarbonic ether. — Although the constitution of this suostance is 
doubtful, it may be here described. Absolute alcohol is introduced into a 
glass-globe containing chlorocarbonic acid (phosgene gas, p. 131) : the gas is 
absorbed in large quantity, and a yellowish liquid produced, from which 



358 COMPOUND ACIDS CONTAINING 

water separates the chlorocarbonic ether. When freed from water by chlo- 
ride of calcium, and from adhering acid by rectification from litharge, it forms 
a thin, colourless, neutral liquid, which burns with a green flame. Its den- 
sity is 1-133 ; it boils at 202° (94°-5C). The vapour, mixed with a large quan- 
tity of air, has an agreeable odour, but when nearly pure is extremeiy suffo- 
cating. It contains C 6 H 5 C10 4 =C 4 H 5 0,C 2 C10g. The density of the vapour 
is 3-82. 

The action of ammonia, gaseous or liquid, upon this substance, gives rise 
to a very curious product, called by M. Dumas ur ethane ; sal-ammoniac is 
at the same time formed. Urethane is a white, solid, crystallizable body, 
fusible below 212° (100°C), and distilling unchanged, when in a dry state, at 
about 356° (180°C) ; if moisture be present, it is decomposed, with evolution 
of ammonia. Water dissolves this substance very easily ; the solution is not 
affected by nitrate of silver, and yields, by spontaneous evaporation, large 
and distinct crystals. It contains C 6 H 7 N0 4 , or elements of carbonic ether 
and urea, — whence the name. 



COMPOUND ACIDS CONTAINING THE ELEMENTS OF ETHER. 

Sulphovinic acid, C 4 H 5 0,2S0 3 ,HO. — Strong rectified spirit of wine is 
mixed with a double weight of concentrated sulphuric acid ; the mixture is 
heated to its boiling point, and then left to cool. When cold, it is diluted 
with a large quantity of water, and neutralized with chalk ; much sulphate 
of lime is produced. The latter is placed upon a cloth filter, drained, and 
pressed ; the clear solution is evaporated to a small bulk by the heat of a 
water-bath, filtered from a little sulphate, and left to crystallize ; the pro- 
duct is sulphovinate of lime, in beautiful colourless, transparent crystals, con- 
taining CaO,C 4 H 5 0,2S0 3 -f-2HO. They dissolve in an equal weight of cold 
water, and effloresce in a dry atmosphere. 

A similar salt, containing baryta, BaO,C 4 H 5 0,2S0 3 -f-2HO, equally soluble, 
and still more beautiful, may be produced by substituting, in the above pro- 
cess, carbonate of baryta for chalk ; from this substance the hydrated acid 
may be procured by exactly precipitating the base by dilute sulphuric acid, 
and evaporating the filtered solution, in vacuo, at the temperature of the air. 
It forms a sour syrupy liquid, in which sulphuric acid cannot be recognized, 
and is very easily decomposed by heat, and even by long exposure in the 
vacuum of the air-pump. All the sulphovinates are soluble ; the solutions 
are decomposed by ebullition. The lead-salt resembles the barytic com- 
pound. That of potassa, easily made by decomposing sulphovinate of lime 
by carbonate of potassa, is anhydrous ; it is permanent in the air, very solu- 
ble, and crystallizes well. 

Sulphovinate of potassa, distilled with concentrated sulphuric acid, give3 
ether; with dilute sulphuric acid, alcohol: and with strong acetic acid, acetic 
ether. Heated with hydrate of lime or baryta, the sulphovinates yield a sul- 
phate of the base and alcohol. 

Phosphovinic acid, C 4 H 5 0,P0 5 ,2HO. — This acid is bibasic. The baryta- 
salt is prepared by heating to 180° (82-°2C) a mixture of equal weights of 
strong alcohol and syrupy phosphoric acid, diluting this mixture, after the 
lapse of 24 hours, with water, and neutralizing by carbonate of baryta. The 
solution of phosphovinate, separated by filtration from the insoluble phos- 
phate, is evaporated at a moderate temperature. The salt crj'stallizes in bril- 
liant hexagonal plates, which have a pearly lustre, and are more soluble in 
cold than in hot water ; it dissolves in 15 parts of water at 08° (20°C). Tho 



THE ELEMENTS OF ETHER. 359 

crystals contains 2BaO,C 4 H 5 0,P0 5 -(-12HO. From this substance the hydra- 
ted acid may be obtained by precipitating the baryta by dilute sulphuric acid, 
and evaporating the filtered liquid in the vacuum of the air-pump ; it forms 
a colourless, syrupy liquid, of intensely sour taste, which sometimes exhibits 
appearances of crystallization. It is very soluble in -water, alcohol, and 
ether, and easily decomposed by heat when in a concentrated state. The 
phosphovinates of lime, silver, and lead possesses but little solubility ; those 
of the alkalis, magnesia, and strontia are freely soluble. 

Voegeli has lately observed that, by the action of syrupy phosphoric acid 
upon alcohol, together with phosphovinic acid, another acid is formed, to 
which he gives the name phosphobiethylic acid, phosphovinic acid being 
designated by phosphethylic acid. The baryta silver and lead-salt of this 
acid are more soluble than the corresponding phosphovinates. The lead- 
salts aud lime-salts are anhydrous, and contain respectively PbO,2C 4 H 5 0,P0 5 
and CaO,2C 4 H 5 0,P0 5 . 

The former of these salts, when heated to a temperature between 356° 
and 874° (180° and 190°C), yields an aromatic, limpid liquid, which is 
tribasic phosphoric ether, 3C 4 H 5 0,P0 5 . It boils at 288° -5 (142° -5C). Its 
formation is represented by the equation : 2(PbO,2C 4 II 5 0,P0 5 ) = 3C 4 H 5 0,P0 5 
-f2PbO,C 4 H 5 0,P0 5 . 

Oxalovinic Acid, C 4 H 5 0,2C 2 3 .HO. — Oxalic ether is dissolved in anhy- 
drous alcohol, and enough alcoholic solution of caustic potassa added to 
neutralize one-half of the oxalic acid present, whereupon the potassa-salt of 
the new acid precipitates in the form of crystalline scales, insoluble in 
alcohol, but easily dissolved by water. The free acid is obtained as a sour 
and exceedingly instable liquid by the addition of hydrofiuosilicic acid to a 
solution of the preceding salt in dilute alcohol. It forms with baryta a 
•very soluble salt. 

A tartrovinic acid has been described, and many other compounds of the 
same type exist. 



Another, and a different view, is very frequently taken of the substances 
just described, and of many analogous compounds. The sulphovinates, 
phosphovinates, &c, are supposed to possess a constitution resembling that 
of ordinary double salts, one of the bases being a metallic oxide, and the 
second ether. Thus, anhydrous sulphovinate of baryta is written BaO,S0 3 
-j-C 4 H 5 0,S0 3 , or double sulphate of baryta and ether ; hydrated sulphovinic 
acid is HO,S0 3 -j-C 4 H 5 0,S0 3 , or bisulphate of ether. There are, however, 
grave objections against this mode of viewing the subject: in every true 
double salt the characters both of acid and bases remain unchanged ; alum 
gives the reactions of sulphuric acid, of alumina, and of potassa; while in 
sulphovinic acid or sulphovinate not a trace of sulphuric acid can be 
detected by any method short ef actual decomposition, by heat or otherwise. 
If sulphovinate of baryta contain sulphate of baryta ready formed, it is 
very difficult to understand how that salt can be decomposed by an addition 
of sulphuric acid. The student must, however, bear in mind that all views 
of the constitution of complex organic compounds must, of necessity, be to 
a great extent hypothetical, and liable to constant alteration with the 
progress of science. • 



Products of the Decomposition of Sulphovinic Acid by Heat. 

A solution of sulphovinic acid, or, what is equivalent to it, a mixture, in 
due proportions, of oil of vitriol and strong alcohol, undergoes decomposi- 
tion when heated, yielding products which differ with the temperature to 



300 COMPOUND ACIDS CONTAINING 

■which the liquid is subjected. The cause of the decomposition is to be 
traced to the instability of the compound itself, and to the basic power of 
water, and the attraction of sulphuric acid for the latter, in virtue of which 
it determines the production of that substance, and liberates the elements 
of the ether. 

When the sulphovinic acid is so far diluted as to boil at 260° (126° -6C) or 
below, or when a temperature not exceeding this is applied to a stronger 
solution by the aid of a liquid bath, the compound acid is resolved into sul- 
phuric acid, which remains behind in the retort or distillatory vessel, while 
alcohol, and mere traces of ether, are volatilized. 

An acid whose boiling-point lies between 260° and 310° (126-6 and 
154° -5C) is decomposed by ebullition into hydrated sulphuric acid and 
ether, which is accompanied by small quantities of alcohol. 

Lastly, when, by the addition of a large quantity of oil of vitriol, the 
boiling-point of the mixture is made to rise to 320° (160°C) and above, the 
production of ether diminishes, and other substances begin to make their 
appearance, of which the most remarkable is defiant gas. The mixture in 
the retort blackens, sulphurous acid and carbonic acid are disengaged, a 
yellow, oily aromatic liquid passes over, and a coaly residue is left, which 
contains sulphur. The chief and characteristic product is the defiant gas ; 
the others may be considered the result of secondary actions. The three 
modes of decomposition may be thus contrasted : — 

Below 260°— C 4 H 5 0,2S0 3 ,HO-f 2HO = C 4 H 5 0,HO + 2(S0 3 ,HO) 
260°— 310°— C 4 H 5 0,2S0 3 ,HO-f HO = C 4 H 5 -f 2(S0 8 ,HO) 
Above 320°— C 4 H 5 0,2S0 3 ,HO = C 4 H 4 -f 2(SO a ,HO) 

The ether-producing temperature is thus seen to be circumscribed within 
narrow limits ; in the old process, however, in which a mixture of equal' 
weights of alcohol and sulphuric acid is subjected to distillation, these con- 
ditions can be but partially complied with. At first the temperature of the 
mixture is too low to yield ether in any quantity, and towards the end of the 
process, long before all the suphovinic acid has been decomposed, it becomes 
too high, so that olefiant gas and its accompanying products appear instead. 
The remedy to this inconvenience consists in restraining the temperature of 
ebullition of the mixture within its proper bounds by the introduction of a 
constant supply of alcohol, to combine with the liberated sulphuric acid, and 
reproduce the sulphovinic acid as fast as it becomes destroyed. The im- 
proved, or continuous ether-process, in which the same acid is made to ethe- 
rify an almost indefinite quantity of spirit, may be thus elegantly conducted 
upon a small scale. 

A wide-necked flask is fitted with a sound cork, perforated by three aper- 
tures, one of which is destined to receive a thermometer, with the graduation 
on the stem ; a second, the vertical portion of a long narrow tube, termina- 
ting in an orifice of about -^ of an inch in diameter ; and the third, a wide 
bent tube, connected with "the condenser, to carry off the volatile products. 
A mixture is made of 8 parts by weight of concentrated sulphuric acid, and 
5 parts of rectified spirit of wine, of about 0-834 sp. gr. This is introduced 
into the flask, and heated by a lamp. The liquid soon boils, and the ther- 
mometer very shortly indicates a temperature of 300° (149°C) ; when this 
happens, alcohol of the above density is suffered slowly to enter by the 
narrow tube, which is put in communication with a reservoir of that liquid, 
consisting of a large bottle perforated by a hole near the bottom, and fur- 
nished with a small brass stop-cock, fitted by a cork ; the stop-cock is secured 
to the end of the long tube by a caoutchouc connecter, tied, as usual with 
silk cord. As the tube passes nearly to the bottom of the flask, the alcohol 
gets thoroughly mixed with the acid liquid, the hydrostatic pressure of the 



THE ELEMENTS OF ETHER, 
Fig. 166. 1 



361 




fluid column being sufficient to ensure the regularity of the flow ; the quan- 
tity is easily adjusted by the aid of the stop-cock. For condensation, a 
Liebig's condenser may be used, supplied with ice-water. The arrangement 
is figured above (fig. 166). 

The intensity of heat, and the supply of alcohol, must be so adjusted that 
the thermometer may remain at 300° (149°C), or as near that temperature 
as possible, while the contents of the flask are maintained in a state of rapid 
and violent ebullition — a point of essential importance. Ether and water 
distil over together, and collect in the receiver, forming two distinct strata ; 
the mixture slowly blackens, from some slight secondary action of the acid 
upon the spirit, or upon the impurities in the latter, but retains, after many 
hours' ebullition, its etherifying powers unimpaired. The acid, however, 
slowly volatilizes, partly in the state of oil of wine, and the quantity of liquid 
in the flask is found, after the lapse of a considerable interval, sensibly 
diminished. This loss of acid constitutes the only limit to the duration of 
the process, which might otherwise continue indefinitely. 

On the large scale, the flask may be replaced by a vessel of lead, the tubes 

1 Fig. 166. Apparatus for the preparation of ether, a. Flask containing the mixture of oil 
of vitriol and alcohol, b. Reservoir -with stop-cock, for supplying a constant stream of alcohol. 
c. Wide hent tube connected with the condenser for conveying away the vapours, d. Th« 
thermometer for regulating the temperature of the boiling liquid. 
ox 



362 OLEJIANT GAS. 

being also of the same metal ; the stem of the thermometer may he made ta 
pass air-tight through the cover, and heat may, peimaps, be advantageously 
applied by high-pressure steam, or hot oil, circulating in a spiral of metal 
tube, immersed in the mixture of acid and spirit. 

The crude ether is to be separated from the water on -which it floats, agi- 
tated ■with a little solution of caustic potassa, and re-distilled by the heat of 
warm water. The aqueous portion, treated with an alkaline solution, and 
distilled, yields alcohol, containing a little ether. Sometimes the spontaneous 
separation before mentioned does not occur, from the accidental presence of 
a larger quantity 7 than usual of undecomposed alcohol ; the addition of a little 
water, however, always suffices to determine it. 

We shall once more return to the formation of ether, when we discuss the 
methyl-compounds. 

Heavy oil of wine. — When a mixture of 2 \ parts of concentrated sulphu- 
ric acid, and 1 part of rectified spirit of wine, of 0-833 sp. gr., is subjected 
to distillation, a little ether comes over, but is quickly succeeded by a yel- 
lowish, oily liquid, which may be freed from sulphurous acid by agitation 
with water, and from ether and undecomposed alcohol by exposure in the 
vacuum of the air-pump, beside two open capsules, the one containing hy- 
drate of potassa, and the other concentrated sulphuric acid. This substance 
may be prepared in larger quantity by the destructive distillation of dry sul- 
phovinate of lime ; alcohol, oil of wine, and a small quantity of an exceed- 
ingly volatile liquid, yet imperfectly examined, are produced. Pure oil of 
wine is colourless, or greenish, of oily consistence, and heavier than water ; 
it has an aromatic taste, and an odour resembling that of peppermint. Its 
boiling point is tolerably high. It is soluble in alcohol and ether, but 
scarcely so in water. By analysis it is found to contain C 8 H O,2SO 3 , or per- 
haps C 4 H 4 ,S0 3 +C 4 H 5 0,S0 3 ; that is, neutral sulphate of ether, in combina- 
tion with the sulphate of a hydro-carbon, etherole. 

In contact with boiling water, oil of wine is resolved into sulphovinic acid, 
and a volatile liquid, known by the name of light, or sweet oil of wine ; with 
an alkaline solution, this effect is produced even with greater facility. Light 
oil of wine, left in a cool place for several days, deposits crystals of a white 
solid matter, which is tasteless, and has but little odour ; it is called etherin. 
The fluid residual portion is yellowish, oily, and lighter than water; it has 
a high boiling-point, solidifies at a very low temperature, and is freely soluble 
in alcohol and ether; it bears the name of etherole. Both etherole and etherin 
have the same composition, namely C 4 H 4 , and are consequently isomeric with 
defiant gas. 

Olefiant gas ; ethyline. — This substance may also be advantageously 
prepared on the principle described, by restraining the temperature within 
certain bounds, and preventing the charring and destruction of the alcohol, 
which always occurs in the old process, and which, at the same time, leads 
to the production of sulphurous and carbonic acids, which contaminate 
the gas. 

If the vapour of alcohol be passed into somewhat diluted sulphuric acid, 
maintained at a boiling-heat, it is absorbed with production of sulphovinic 
acid, which is shortly afterwards decomposed into water and olefiant gas. 
The process is thus conducted : — A wide-necked flask (fig. 167), containing 
rectified spirit of wine, is fitted with a cork, through which pass an ordinary 
safety-tube, with a little water, and the bent glass tube, intended to convey 
the vapour of the spix'it into the acid. The latter must be of such strength, 
as to have a boiling-point between 320° and 330° (160° and 165°-5C) ; it is 
prepared by diluting strong oil of vitriol with rather less than half its weight 
of water. The acid is placed in a second and larger flask, also closed by a 
cork, into which are inserted two tubes and a thermometer. The first is y 



DUTCH-LIQUID 
Fig. 167. 




Fig. 168. 



piece of straight tube, wide enough to allow the tube conveying the alcohol- 
vapour to pass freely down it, and dipping a little way into the acid ; the 
second is a narrow bent tube, the extremity of which is immersed in the 
water of the pneumatic trough. Both flasks are 
heated ; and as soon as it is seen that the acid is in a. 
state of tranquil ebullition, while the thermometer 
marks the temperature above mentioned, the spirit is 
made to boil, and its vapour carried into the acid, 
which very soon begins to evolve defiant gas and 
vapour of water, accompanied by a little ether and oil 
of wine, but no sulphurous acid. The acid liquid does 
not blacken, and the experiment may be carried on as 
long as may be desired. This is a very elegant and 
instructive, although somewhat troublesome, method 
of preparing the gas. The essential parts of the 
apparatus are shown in fig. 167. 

Chloride of olefiant gas ; Dutch-liquid. — It 
has long been known that when equal measures of 
olefiant gas and chlorine are mixed over water, absorp- 
tion of the mixture takes place, and a yellowish oily 
liquid is produced, which collects upon the surface of 
the water, and ultimately sinks to the bottom in drops. 
It may be easily prepared, in quantity, by causing 
the two gases to combine in a glass globe, fig. 168, 
having a narrow neck at the lower part, dipping into 
a small bottle, destined to receive the product. The 
two gases are conveyed by separate tubes, and 
allowed to mix in the globe, the olefiant gas being 




364 CHLORIDES Or CARBON. 

kept a little in excess. The chlorine should be washed with water, and the 
olefiant gas passed through strong oil of vitriol, to remove vapour of ether ; 
the presence of sulphurous and carbonic acids is not injurious. Combina- 
tion takes place very rapidly, and the liquid product trickles down the sides 
of the globe into the receiver. When a considerable quantity has been col- 
lected, it is agitated first with water, and afterwards with concentrated sul- 
phuric acid ; it is, lastly, purified by re-distillation. If impure olefiant gas 
be employed, the crude product contains a large quantity of a substance 
called by M. Rcgnault chloro-sulphuric acid, S0 2 C1, which, on contact with 
water, is converted, by the decomposition of the latter, into sulphuric and 
hydrochloric acids. 

Pure Dutch-liquid is a thin, colourless liquid, of agreeably fragrant odour, 
and sweet taste ; it is slightly soluble in water, and readily so in alcohol and 
ether. It is heavier than water, and boils when heated to 180° (82° -3C) ; 
it is unaffected by oil of vitriol and solid hydrate of potassa. When in- 
flamed, it burns with a greenish, smoky light. This substance yields, by 
analysis, C 4 H 4 C1 2 . 

When Dutch-liquid is treated with an alcoholic solution of caustic potassa, 
it is slowly resolved into chloride of potassium, which separates, and into a 
new and exceedingly volatile substance, containing C 4 H 3 C1, whose vapour 
requires to be cooled down to 0° ( — 17°-7C) before it condenses. At this 
temperature it forms a limpid, colourless liquid. Chlorine is absorbed by 
this substance, and a compound produced, which contains C 4 H 3 C1 3 ; this is 
in turn decomposed by an alcoholic solution of hydrate of potassa into 
chloride of potassium and a new volatile liquid, C 4 H 2 C1 2 . 

Bromide and iodide of olefiant gas, C 4 H 4 Br 2 and C 4 H 4 I 2 . — These 
compounds correspond to Dutch-liquid ; they are produced by bringing 
olefiant gas in contact with bromine and iodine. The bromide is a colour- 
less liquid, of agreeable, ethereal odour, and has a density of 2-16; it boils 
at 265° (129°-5C), and solidifies, when cooled, to near 0° (— 17°-7C). The 
iodide is a colourless, crystalline, volatile substance, of penetrating odour ; 
it melts at 174° (78°-8C), resists the action of sulphuric acid, but is decom- 
posed by caustic potassa. 

Products of the action of chlorine on dutch-liquid ; chlorides 
of carbon. — Dutch-liquid readily absorbs chlorine gas, and yields several 
new compounds, produced by the abstraction of successive portions of 
hydrogen, and its replacement or substitution by equivalent quantities of 
chlorine. This regular substitution of chlorine, bromine, iodine, &c, in 
place of hydrogen, as before stated, is a phenomenon of constant occur- 
rence in reactions between these bodies and very many organic compounds. 
In the present case four such steps may be traced, giving rise, in each 
instance, to hydrochloric acid and a new substance. Three out of the four 
new products are volatile liquids, containing C 4 H 3 C1 3 ,C 4 H 2 C1 4 and C 4 IIC1 5 ; 
the fourth C 4 C1 6 in which the substitution of chlorine for hydrogen is com- 
plete, is the chloride of carbon, long ago obtained by Mr. Faraday by putting 
Dutch-liquid into a vessel of chlorine gas, and exposing the whole to the 
influence of light. 

Scsquichloride or Perchloride of^ Carbon, C 4 C1 6 , is a white, solid, crystalline 
substance, of aromatic odour, insoluble in water, but easily dissolved by 
alcohol and ether; it melts at 320° (160°C), and boils at a temperature a 
little above. It burns with difficulty, and is unaffected by both acids and 
alkalis. It is prepared as above stated. 

Protochloride of Carbon, C 4 C1 4 .— When the vapour of the preceding sub- 
stance is transmitted through a red-hot porcelain tube filled with fragments 
of glass or rock-crystal, it is decomposed into free chlorine, and a second 
chloride of carbon, which condenses in the form of a volatile, colourless 



ETHIONIC AND ISETHIONIC ACIDS. 365 

liquid, which has a density of 1-55, and boils at 248° (120°C). The density 
ot its vapour is 5-82. It resembles in chemical relations the perchloride. 

Subchloride of Carbon, C 4 C1 2 , is produced when the protochloride is passed 
many successive times through an ignited porcelain tube ; it is a white, 
volatile, silky substance, soluble in ether. 

Bichloride of Carbon, C 2 C1 4 . — A fourth chloride of carbon is known and will 
be described here, although it is not derived from the alcohol group. It is 
formed by passing the vapour of bisulphide of carbon together with chlo- 
rine, through a red-hot porcelain-tube. A mixture of chloride of sulphur 
and bichloride of carbon is formed, which is distilled with potassa, when 
the chloride of sulphur is decomposed, and pure bichloride passes over. It 
is a colourless liquid of 1-56 sp. gr., and boils at 170 o, 6 (77°C). An alco- 
holic solution of potassa converts this compound into a mixture of chloride 
of potassium and carbonate of potassa. The same compound is formed by 
exhausting the action of chlorine upon marsh-gas and chloride of methyl in 
the sunshine. 

Combustible platinum-salts of Zeise. — A solution of bichloride of pla- 
tinum in alcohol is mixed with a little chloride of potassium dissolved in hy- 
drochloric acid, and the whole digested some hours at a high temperature. 
The alcohol is distilled off, the acid residue neutralized by carbonate of 
potassa, and left to crystallize. The distilled liquid contains hydrochloric 
ether and aldehyde. The platinum-salt forms yellow, transparent, prismatic 
crystals, which become opaque on heating from loss of water ; when intro- 
duced into the flame of a spirit lamp, the salt burns vividly, leaving metallic 
platinum. It is soluble in 5 parts of warm water. When dried at 212° 
(100°C), this substance contains Pt 2 Cl2,C 4 H 4 -|-KCl. Corresponding com- 
pounds, containing Pt 2 Cl 2 ,C 4 H 4 -f NaCl, and Pt 2 Cl 2 ,C 4 H 4 -j-NH 4 Cl, are known 
to exist. 

The chloride of potassium can be separated from the above compound by 
the cautious addition of bichloride of platinum ; the filtered solution yields 
by evaporation in vacuo a yellow, gummy, acid mass. The solution is slowly 
decomposed in the cold, and rapidly at a boiling heat, with separation of a 
black precipitate. These compounds are of uncertain constitution. 



PRODUCTS OF THE ACTION OF ANHYDROUS SULPHURIC ACID ON ALCOHOL 
AND OLEFIANT GAS. 

"When anhydrous alcohol is made to absorb the vapour of anhydrous sul- 
ohuric acid, a white, crystalline, solid substance is produced, fusible at a 
gentle heat, which, when purified from adhering acid, is found to consist of 
carbon, hydrogen, and the elements of sulphuric acid, in the relation of the 
equivalent numbers, or probably C 4 H 4 ,4S0 3 . To this substance Magnus 
applies the name sulphate of carbyl. A body very similar in appearance and 
properties, and probably identical with this, had previously been produced 
by M. Regnault, by passing pure and dry olefiant gas over anhydrous sul- 
phuric acid contained in a bent tube. 

When the crystals of sulphate of carbyl are dissolved in alcohol, watev 
added, the whole neutralized by carbonate of baryta, and the filtered solu- 
tion concentrated by very gentle heat to a small bulk, and then mixed with 
a quantity of alcohol, a precipitate falls, which consists of baryta, in com- 
bination with a peculiar acid closely resembling the sulphovinic, but yet 
differing in many important particulars. Bv the cautious addition of dilute 
31* 



366 CHLORAL. 

sulphuric acid, the base may be withdrawn, and the hydrate of the new acid 
left, in solution ; it bears the name of elhionic acid, and contains C 4 H 5 0,4S0 3 -(- 
2110. The etbionates differ completely from the sulphovinates ; all are soluble 
in water, and appear to be anhydrous. Those of lime, baryta, and oxide of 
lead refuse to crystallize ; the ethionates of potassa, soda, and ammonia, on 
the contrary, may readily be obtained in good crystals. 

When a solution of ethionic acid is boiled, it is decomposed into sulphuric 
acid, and a second new acid, the isethionic, isomeric with sulphovinic acid. 
The isethionic acid and its salts are very stable: their solutions maybe 
boiled without decomposition. The isethionates of baryta, lead, copper, 
potassa, soda, and ammonia crystallize with facility, and cannot be confounded 
with the sulphovinates. The hydrated acid contains C 4 H 5 0,2S0 3 -4-HO. 

The action of anhydrous sulphuric acid on ether, as has been already men- 
tioned, gives rise to the formation of neutral sulphate of ethyl (see page 354.) 
Together with this substance sulphuric acid and several other acids methionic 
and althionic are obtained, which are not yet sufficiently studied. 



PRODUCTS OF THE ACTION OF CHLORINE ON ALCOHOL, ETHER, AND ITS 
COMPOUNDS. 

Chloral. — Perfectly dry chlorine is passed into anhydrous alcohol to 
saturation ; the gas is absorbed in large quantity, and hydrochloric acid 
abundantly produced. Towards the end of the process the reaction must be 
aided by heat. When no more hydrochloric acid appears, the current of 
chlorine is interrupted, and the product agitated with three times its volume 
of concentrated sulphuric acid ; on gently warming this mixture in a water- 
bath, the impure chloral separates as an oily liquid, which floats on the 
sui-face of the acid ; it is purified by distillation from fresh oil of vitriol, and 
afterwards from a small quantity of quick-lime, which must be kept com- 
pletely covered by the liquid, until the end of the operation. Chloral has 
been obtained from starch, by distillation with hydrochloric acid and binoxide 
of manganese. 

Chloral is a thin, oily, colourless liquid, of peculiar and penetrating odour, 
which excites tears; it has but little taste. When dropped upon paper it 
leaves a greasy stain, which is not, however, permanent. It has a density 
of 1-502, and boils at 201°-2 (94°C). Chloral is freely soluble in water, 
alcohol, and ether ; it forms, with a small quantity of water, a solid, crystal- 
line hydrate ; the solution is not affected by nitrate of silver. Caustic baryta 
and lime decompose the vapour of chloral when heated in it with appearance 
of ignition ; the oxide is converted into chloride, carbon is deposited, and car- 
bonic oxide set free. Solutions of caustic alkalis also decompose it, with 
production of a formate of the base, and a new volatile liquid, chloroform. 
Chloral contains C 4 HC1 3 2 . 

When chloral is preserved for any length of time, even in a vessel herme- 
tically sealed, it undergoes a very extraordinary change; it becomes con- 
verted into a solid, white, translucent substance, insoluble chloral, possessing 
exactly the same composition as the liquid itself. The new product is but 
very slightly soluble in water, alcohol, or ether ; when exposed to heat, alone 
or in contact with oil of vitriol, it is re-converted into ordinary chloral. So- 
lution of caustic potassa resolves it into formic acid and chloroform. Bro- 
mine acts upon alcohol in the same manner as chlorine, and gives rise to a 
product very similar in properties to the foregoing, called brtmal, which con. 



ALCOHOL. 367 

tains C 4 HBr 3 2 . It forms a crystallizable hydrate with water, and is decom- 
posed by strong alkaline solutions into formic acid and bromoform. A cor- 
responding iodine-compound probably exists. 

Chlorine acts in a different manner upon alcohol which contains water ; 
when very dilute, the principal products are hydrochloric acid and aldehyde, 
the change being one of oxidation at the expense of the water. With strong 
spirit the reaction is more complex, one of its products being a volatile, oily, 
colourless liquid, of uncertain composition, long known under the name of 
heavy muriatic ether. 

The mode of action of dry chlorine on pure ether conforms strictly to the 
law of substitution before mentioned ; the carbon remains intact, while a 
portion or the whole of the hydrogen is removed, and its place supplied by 
an equivalent quantity of chlorine. Ether exposed to a current of the dry 
gas for a considerable period, the temperature being at first artifically 
reduced, yields a heavy oily product, having the odour of fennel. This is 
found by analysis to contain C 4 H 3 C] 2 0, or ether, in which 2 eq. of chlorine 
have been substituted for 2 eq. of hydrogen. It may be termed bichlori- 
netted ether. By the farther action of chlorine, aided by sunlight, the re- 
maining hydrogen is removed, and a white crystalline solid substance, closely 
resembling sesquichloride of carbon produced. This is composed of C 4 C1 5 ; 
it is called pentachlorinetted ether. In a substance called cloretheral, 
C 4 H 4 C10, accidentally formed by M. d'Arcet, in the preparation of Dutch- 
liquid, from the ether-vapour mixed with the defiant gas, we have evidently 
the first member of this series. 

With the compound ethers, the same remarkable law is usually followed. 
The change is, however, often complicated by the appearance of secondary 
products. Thus, chlorinetted acetic ether, a dense, oily liquid, very different 
from common acetic ether, was found to contain CgHgClgO,,, being a substi- 
tution product of CgM 8 4 =C 4 H 5 0,C 4 H 3 3 ; and chlorinetted formic ether, 
C 6 H 4 C1 2 4 , is formed, in like manner, by the substitution of 2 eq. chlorine 
for 2 eq. hydrogen in ordinary formic ether, C 6 B 6 4 =C 4 H 5 0,C 2 H0 3 . A 
most remarkable and interesting set of componnds, due to substitution of 
this kind, are formed by the action of chlorine on chloride of ethyl, or light 
hydrochloric ether. When the vapour of this substance is brought into con- 
tact with chlorine gas, the two bodies combine to a colourless oily liquid, 
very like Butch-liquid, but yet differing from it in several important points ; 
it has, however, precisely the same composition, and its vapour has the same 
density. By the prolonged action of chlorine three other compounds are 
successively obtained, each poorer in hydrogen and richer in chlorine than 
the pi*eceding, the ultimate product being the well-known sesquichloride of 
carbon of Mr. Faraday. 

Hydrochloric ether C 4 H 5 C1 

Monochlorinetted hydrochloric ether C 4 H 4 C1 2 

Bichlorinetted C 4 H 3 C1 3 

Trichlorinetted C 4 H 2 C1 4 

Quadrichlorinetted C 4 H Cl 5 

Sesquichloride of carbon C 4 Cl 6 



DERIVATIVES OE ALCOnOL CONTAINING SULPHUR. 

Mercaptan. — A solution of caustic potassa, of 1-28 or 1-3 sp. gr., is satu 
rated with sulphuretted hydrogen, and mixed in a retort with an equal volume 
of solution of sulphovinate of lime of the same density. The retort Is con- 



068 ALCOHOL. 

nected with a good condenser, and heat is applied by means of a hath of salt 
and water. Mercaptan and water distil over together, and are easily sepa- 
rated by a funnel. The product thus obtained is a colourless, limpid liquid, 
of sp. gr. 0-842, but slightly soluble in water, easily miscible, on the con- 
trary, with alcohol. It boils at 97° (36°C). The vapour of mercaptan has 
a most intolerable odour of onions, which adheres to the clothes and person 
with great obstinacy ; it is very inflammable, and burns with a blue flame. 
Mercaptan contains C 4 H 6 S 2 =C 4 H 5 S,HS ; or alcohol, having sulphur in the 
place of oxygen. 

When brought into contact with red oxide of mercury, even in the cold, 
violent reaction ensues, 1 water is formed, and a white substance is produced, 
soluble in alcohol, and separating from that liquid in distinct crystals, which 
contain C 4 H 5 S,HgS. This compound is decomposed by sulphuretted hydro- 
gen, sulphide of mercury being thrown down, and mercaptan reproduced. 
By adding solutions of the oxides of lead, copper, silver, and gold, to an 
alcoholic solution of mercaptan, corresponding compounds containing those 
metals are formed. Caustic potassa produces no effect upon mercaptan, but 
potassium displaces hydrogen, and gives rise to a crystallizable compound 
soluble in water. 

Xanthig acid. — The elements of ether and those of bisulphide of carbon 
combine in presence of an alkali to a very extraordinary substance, possess- 
ing the properties of an oxygen-acid, to which the name xanthic is applied, 
un account of the yellow colour of one of its most permanent and charac- 
teristic salts, that of oxide of copper. Hydrate of potassa is dissolved in 
12 parts of alcohol of 0-800 sp. gr. ; into this solution bisulphide of carbon 
is dropped until it ceases to be dissolved, or until the liquid loses its alka- 
linity. The whole is then cooled to 0° ( — 17° -8C), when the potassa-salt 
separates in the form of brilliant, slender, colourless prisms, which must be 
quickly pressed between folds of bibulous paper, and dried in vacuo. It is* 
freely soluble in water and alcohol, but insoluble in ether, and is gradually 
destroyed by exposure to air by oxidation of a part of the sulphur. Hy- 
drated xanthic acid may be prepared by decomposing the foregoing com- 
pound by dilute sulphuric or hydrochloric acid. It is a colourless, oily 
liquid, heavier than water, of powerful and peculiar odour, and very com- 
bustible ; it reddens litmus-paper, and ultimately bleaches it. Exposed to 
gentle heat, it is decomposed into alcohol and bisulphide of carbon ; this 
happens at a temperature of 75° (23°-8C). Exposed to the air, or kept be- 
neath the surface of water open to the atmosphere, it becomes covered with 
a whitish crust, and is gradually destroyed. The xanthates of the alkalis 
and of baryta are colourless and crystallizable ; the lime-salt dries up to a 
gummy mass ; the xanthates of the oxides of zinc, lead, and mercury are 
white, and but feebly soluble, that of copper is a flocculent, insoluble sub- 
stance, of beautiful yellow colour. 

Hydrated xanthic acid contains C 6 H5S 4 0,HO ; or C 4 H 5 0,C 2 S 4 ,HO. In the 
salts this water is replaced by one equivalent of a metallic oxide. 



DERIVATIVES OF ALCOHOL CONTAINING METALS. 

Zinc-ethyl. — In heating iodide of ethyl with zinc in sealed glass-tubes 
(see compound ethers; ethyl-theory, p. 352) a white substance remains in 
the tube, which is a mixture of iodide of zinc and a peculiar volatile com- 



"Whence the name, mercurium captans. 



ALCOHOL. 369 

pound, to which Dr. Frankland has given the name zinc-ethyl. It may be 
separated from the residue by distilling it in a current of hydrogen, when it 
it is obtained in the form of a liquid of a disagreeable odour, which contains 
C 4 H 5 Zn. In contact with atmospheric air it is rapidly oxidized. When 
mixed with water, this compound is decomposed with evolution of a carbo- 
netted hydrogen, having the formula C 4 H 6 =C 4 H 5 ,H, which may be viewed 
as the hydride of ethyl. 

Stibethyl. — Iodide of ethyl when distilled with an alloy of antimony and 
potassium, yields a curious substance, which MM. Loewig and Schweizer 
have described under the name of stibethyl. It contains SbC 12 H ]5 =Sb 3 
(C 4 H 5 ). We shall return to this substance when speaking of the compound 
ammonias. 1 



PRODUCTS OF THE OXIDATION OF ALCOHOL. 

When alcohol and ether burn with flame in free air, the products of their 
combustion are, as with all bodies of like chemical nature, carbonic acid and 
water. Under peculiar circumstances, however, these substances undergo 
partial oxidation, in which the hydrogen alone is affected, the carbon re- 
maining untouched. The result is the production of certain compounds, 
which form a small series, supposed by some chemists to contain a common 
radical, to which the name acetyl is applied. It is derived from ethyl by the 
oxidation and removal of 2 eq. of hydrogen. 

Table of Acetyl- Compounds. 

Acetyl (symbol Ac) C 4 K 3 

Oxide of acetyl (unknown) C 4 H 3 

Hydrate of oxide of acetyl; aldehyde C 4 H 3 0,HO 

Acetylous acid ; aldehydic acid C 4 H 3 2 ,HO 

Acetylic acid ; acetic acid C 4 H 3 3 ,HO 

Acetyl and its protoxide are alike hypothetical. 

Aldehyde, C 4 H 4 2 or AcO,HO. — This substance is formed, as already no- 
ticed, among other products, when the vapour of ether or alcohol is trans- 
mitted through a red-hot tube; also, by the action of chlorine on wealr. 
alcohol. It is best prepared by the following process : — G parts of oil of 
vitriol are mixed with 4 parts of rectified spirit of wine, and 4 parts of 
water ; this mixture is poured upon 6 parts of powdered binoxide of man- 
ganese, contained in a capacious retort, in connection with a condenser, 
cooled by ice-cold water. Gentle heat is applied ; and when 6 parts of liquid 
have passed over, the process is interrupted. The distilled product is put 
into a small retort, with its own weight of chloride of calcium, and redis- 
tilled; the operation is repeated. The aldehyde, still retaining alcohol, and 
other impurities, is mixed with twice its volume of ether, and saturated 
with dry ammoniacal gas ; a crystalline compound of aldehyde and ammonia 
separates, which may be washed with a little ether, and dried in the air. 
From this substance the aldehyde may be separated by distillation in a 
water-bath, with sulphuric acid, diluted with an equal quantity of water ; 
by careful rectification from chloride of calcium, at a temperature not ex- 
ceeding 87° (30 o, 5C), it is obtained pure and anhydrous. 

1 Bismaethyl, BiCj2H !5 =Bi 3(C 4 H5). Stanethyl, SnC 4 Hs and tellurethy], TeC4lI 5 have also 
been produced by similar reactions and some of their compounds investigated. — R. B. 



870 ALDEIIYDIC ACID. 

Aldehyde » is a limpid, colourless liquid, of characteristic ethereal odour, 
•which, when strong, is exceedingly suffocating. It has a density of 0-790, 
boils at 72° (22°-3C), and mixes, in all proportions, with water, alcohol, and 
ether; it is neutral to test-paper, but acquires acidity on exposure to air, 
from the production of acetic acid ; under the influence of platinum-black 
this change is very speedy. When a solution of this compound is heated 
with caustic potassa, a remarkable brown, resin-like substance is produced, 
the so-called aldehyde-resin. Gently heated with protoxide of silver, it reduces 
the latter without evolution of gas, the metal being deposited on the inner 
surface of the vessel as a brilliant and uniform film ; the liquid contains alde- 
hydate of silver. 

When treated with hydrocynic acid, aldehyde yields a substance called 
alanine, which was already noticed, when treating of lactic acid, and which 
will be described more in detail in the section on vegeto-alkalis, under the 
head of bases from aldehyde. 

The action of sulphuretted hydrogen upon the ammonia-compound gives 
rise to the formation of thialdine, noticed likewise under the head of bases 
from aldehyde. 

The ammonia-compound above mentioned forms transparent, colourless 
crystals of great beauty ; it has a mixed odour of ammonia and turpentine ; 
it dissolves very easily in water, with less facility in alcohol, and with diffi- 
culty in ether; it melts at about 170° (76°C), and distils unchanged at 212° 
(100°C). Acids decompose it, with production of ammoniacal salt and sepa- 
ration of aldehyde. The crystals, which are apt to become yellow, and lose 
their lustre in the air, contain C 4 H 4 2 -f-NH 3 . 

When pure aldehyde is long preserved in a close-stopped vessel, it is 
sometimes found to undergo spontaneous change into one, and even two iso- 
meric modifications, differing completely in properties from the original 
compound. In a specimen kept some weeks at 32° (0°C), transparent acicular 
crystals were observed to form in considerable quantity, which, at a tempe- 
rature little exceeding that of the freezing-point of water, melted to a colour- 
less liquid, miscible with water, alcohol, and ether ; a few crystals remained, 
which sublimed without fusion, and were probably composed of the second 
substance. This new body received the name elaldehyde; it was found to be 
identical in composition with aldehyde, but to differ in properties and in the 
density of its vapour ; the latter has a sp. gr. of 4-515, while that of alde- 
hyde is only 1-532, or one-third of that number. It refuses to combine with 
ammonia, is not rendered brown by potassa, and is but little affected by 
solution of silver. 

The second modification, or metaldehyde, is sometimes produced in pure 
aldehyde, kept at the common temperature of the air, even in hermetically- 
sealed tubes ; the conditions of its formation are unknown. It forms colour- 
less, transparent, prismatic crystals, which sublime without fusion at a 
temperature above 212° (100°), and are soluble in alcohol and ether, but not 
in water. They also were found, by analysis, to have the same composition 
as aldehyde. The substance which we have described by the term of chloral 
may be viewed as bichlorinetted aldehyde. 

Aldehydic acid, C 4 H 3 2 ,HO. — When solution of aldehydate of silver, 
obtained by digesting oxide of silver in excess with aldehyde, is precipitated 
n>y sulphuretted hydrogen, an acid liquid is obtained, which neutralizes 
alkalis, and combines with the oxides of the metals. It is very easily decom- 
posed. Aldehydate of silver, mixed with baryta-water, gives rise to aldehy- 
date of baryta and oxide of silver : if this precipitate be heated in the liquid, 

1 Alcoliol dehydrogcnatus. 



ACETIC ACID. 371 

the metal is reduced, and neutral acetate of baryta formed ; whence it is in- 
ferred that the new acid contains the elements of the acetic acid, minus an 
equivalent of oxygen. 

Acetal. — This substance is one of the products of the slow oxidation of 
alcohol-vapour under the influence of platinum-black. Spirit of wine is 
poured into a large, tall, glass-jar, to the depth of about an inch, and a 
shallow capsule, containing slightly -moistened platinum -black, arranged 
above the surface of the liquid ; the jar is loosely covered by a glass plate, 
and left during two or three weeks, in a warm situation. At the expiration 
of that period the liquid is found highly acid; it is to be neutralized with 
carbonate of potassa, as much chloride of calcium added as the liquid will 
dissolve, and the whole subjected to distillation, the first fourth only being 
collected. Fused chloride of calcium added to the distilled product now 
throws up a light oily liquid, which is a mixture of acetal with alcohol, 
aldehyde, and acetic ether. By fresh treatment with ^chloride of calcium, 
and long exposure to gentle heat in a retort, the aldehyde is expelled. The 
acetic ether is destroyed by caustic potassa, and the alcohol removed by 
washing with water, after which the acetal is again digested with fused 
chloride of calcium, and re-distilled. 

Pure acetal is a thin, colourless fluid, of agreeable ethereal odour of sp. 
gr. 0-821 at 72° (22°-2C), and boiling at 220° (104°C). It is soluble in 18 
parts of water, and miscible in all proportions with alcohol and ether. It is 
unchanged in the air ; but, under the influence of platinum-black, becomes 
converted into aldehyde, and eventually into acetic acid. Nitric and chromic 
acids produce a similar effect. Strong boiling solution of potassa has no 
action on this substance. Acetal contains C 12 H 34 4 , or the elements of 2 eq. 
ether and 1 eq. aldehyde, C 12 H, 4 4 =2C 4 ?I 5 0+C 4 H 4 2 . 

When a coil of fine platinum wire is heated to redness, and plunged into 
a mixture of ether, or alcohol-vapour and atmospheric air, it determines 
upon its surface the partial combustion of the former, and gives rise to an 
excessively pungent acrid vapour, which may be con- 
densed to a colourless liquid by suitable means. The Fig- 169- 
heat evolved in the act of oxidation is sufficient to main- 
tain the wire in an incandescent state. The experiment / ~~7 
may be made by putting a little ether into an ale-glass, / * jf 
fig. 169, and suspending over it the heated spiral from f^JWsSi 
a card ; or by slipping the coil over the wick of a spirit- u " ' M[\!MS 
lamp, so that the greater part may be raised above the \ Mlfff 
cotton; the lamp is supplied with ether or spirit of \ ^'» 
wine, lighted for a moment, and then blown out. The \ |f 
coil continues to glow in the mixed atmosphere of air vs^# 
and combustible vapour, until the ether is exhausted. iPT 
This is the lamp without flame of Sir H. Davy. A ball s'/\~~*S 
of spongy platinum may be substituted for the coil of Qj~^L^) 
Wire. The condensed liquid contains acetic and formic S;5 === c0 ^ 
acids with aldehyde and aldehydic acid. 

Acetic Acid. — Pure alcohol, exposed to the air, or thrown into a vessel 
of oxygen gas, fails to suffer the slightest change by oxidation ; when 
diluted with water, it remains also unaffected. If, on the other hand, spirit 
of wine be dropped upon dry platinum-black, the oxygen condensed into the 
pores of the latter, reacts so powerfully upon the alcohol as to cause its 
instant inflammation. When the spirit is mixed with a little water, and 
slowly dropped upon the finely divided metal, oxidation still takes place, but 
with less energy, and vapour of acetic acid is abundantly evolved. It i? 
almost unnecessary to add, that the platinum itself undergoes no change ic 
this experiment. 



372 ACETIC ACID. 

Dilute alcohol, mixed with a little yeast, or almost any azotized organic 
matter, susceptible of putrefaction, and exposed to the air, speedily becomes 
oxidized to acetic acid. Acetic acid is thus manufactured in Germany, by 
Buffering such a mixture to flow over wood-shavings, steeped in a little vine- 
gar, contained in a large cylindrical vessel, through which a current of air 
is made to pass. The greatly extended surface of the liquid expedites the 
change, which is completed in a few hours. No carbonic acid is produced 
in this reaction. 

The best vinegar is made from wine by spontaneous acidification in a 
partially filled cask to which the air has access. Vinegar is first introduced 
into the empty vessel, and a quantity of wine added ; after some days a 
second portion of wine is poured in, and after similar intervals a third and 
a fourth. When the whole has become vinegar, a quantity is drawn off 
equal to that of the wine employed, and the process is recommenced. The 
temperature of the building is kept up to 86° (30°C). Such is the plan 
adopted at Orleans. 1 In England vinegar of an inferior description is pre- 
pared from a kind of beer made for the purpose. The liquor is exposed to 
the air in half-empty casks, loosely stopped, until acidification is complete. 
A little sulphuric acid is afterwards added, with a view of checking farther 
decomposition, or mothering, by which the product would be spoiled. 

There is another source of acetic acid besides the oxidation of alcohol : 
when dry, hard wood, as oak and beech, is subjected to destructive distilla- 
tion at a red-heat, acetic acid is found among the liquid condensable pro- 
ducts of the operation. The distillation is conducted in an iron cylinder of 
large dimensions, to which a worm or condenser is attached ; a sour watery 
liquid, a quantity of tar, and much inflammable gas pass over, while char- 
coal of excellent quality remains in the retort. The acid liquid is subjected 
to distillation, the first portion being collected apart for the sake of a pecu- 
liar volatile body, shortly to be described, which it contains. The remainder 
is saturated with lime, concentrated by evaporation, and mixed with solu- 
tion of sulphate of soda ; sulphate of lime precipitates, while the acetic 
acid is transferred to the soda. The filtered solution is evaporated to its 
crystallizing-point ; the crystals are drained as much as possible from the 
dark, tarry mother-liquid, and deprived by heat of their combined water. 
The dry salt is then cautiously fused, by which the last portions of tar are 
decomposed or expelled ; it is then re-dissolved in water, and re-crystallized. 
Pure acetate of soda, thus obtained, readily yields hydrated acetic acid by 
distillation with sulphuric acid. 

The strongest acetic acid is prepared by distilling finely powdered anhy- 
drous acetate of soda with three times its weight of concentrated oil of 
vitriol. The liquid is purified by rectification from sulphate of soda, acci- 
dentally thrown up, and then exposed to a low temperature. Crystals of 
h} r drate of acetic acid form in large quantity, which may be drained from 
the weaker fluid portion, and then suffered to melt. Below 60° (15° -5C) 
this substance forms large, colourless, transparent crystals, which above 
that temperature fuse to a thin, colourless liquid, of exceedingly pungent 
and well-known odour; it raises blisters on the skin. It is miscible in all 
proportions with water, alcohol, and ether, and dissolves camphor and 
several resins. When diluted it has a pleasant acid taste. The hydrate of 
acetic acid in the liquid condition has a density of 1-0G3, and boils at 246° 
(119°C) ; its vapour is inflammable. Acetic acid forms a great number of 
exceedingly important salts, all of which are soluble in water ; the acetates 
Df silver and mercury are the least soluble. 

" r 3 3 ,HO = Ac0 3 ,IIO ; it is formed 

1 Dumas, Chimie appliqu6e aux Arts, ri. 537. 



ACETIC ACID. 373 

from alcohol by the substitution of 2 eq. of oxygen for 2 eq. of hy drogen. 
The water is basic, and can be replaced by metallic oxides. A different view 
regarding the constitution of this acid has been proposed by Prof. Kolbe; it 
is chiefly based upon the remarkable decomposition which acetic acid under- 
goes when submitted to the action of the galvanic current. We shall return 
to this subject when speaking of valerianic acid. 

Dilute acetic acid, or distilled vinegar, used in pharmacy, should always 
be carefully examined for copper and lead ; these impurities are contracted 
from the metallic vessel or condenser sometimes employed in the process. 
The strength of any sample of acetic acid cannot be safely inferred from its 
density, but is easily determined by observing the quantity of dry carbonate 
of soda necessary to saturate a known weight of the liquid. 1 

Acetate of potassa, KO,C 4 H 3 3 . — This salt crystallizes with, great diffi- 
culty; it is generally met with as a foliated, white, crystalline mass, obtained 
by neutralizing carbonate of potassa by acetic acid, evaporating to dryness, 
and heating the salt to fusion. The acetate is extremely deliquescent, and 
soluble in water and alcohol ; the solution is usually alkaline, from a little 
loss of acid by the heat to which it has been subjected. From the alcoholic 
solution, carbonate of potassa is thrown down by a stream of carbonic acid. 

Acetate of soda, NaO,C 4 H 3 Q 3 -f-6HO. — The mode of preparation of this 
salt on the large scale has been already described; it forms large, transpa- 
rent, colourless crystals, derived frum a rhombic prism, which are easily 
rendered anhydrous by heat, effloresce in dry air, and dissolve in 3 parts of 
cold, and in an equal weight of hot water, — it is also soluble in alcohol. The 
taste of this substance is cooling and saline. The dry salt undergoes the 
igneous fusion at 550° (287°-8C), and begins to decompose at 600° (315°-5C). 

Acetate of ammonia; spirit of Mindererus ; NH 4 0,C 4 H 3 3 . — The neu- 
tral solution obtained by saturating strong acetic acid by carbonate of am- 
monia cannot be evaporated without becoming acid from loss of base ; the 
salt passes off in large quantity with the vapour of water. Solid acetate of 
ammonia is best prepared by distilling a mixture of equal parts of acetate of 
lime and powdered salammoniac ; chloride of calcium remains in the retort. 
A saturated solution of the solid salt in hot water, suffered slowly to cool in 
a close vessel, deposits long slender crystals, which deliquesce in the air. 
Acetate of ammonia has a sharp and cooling, yet sweet, taste ; its solution 
becomes alkaline on keeping, from decomposition of the acid. 

Acetate of ammonia when distilled with anhydrous phosphoric acid, loses 
4 eq. of water, being converted into a colourless liquid inmiscible with water, 
of an aromatic odour, and boiling at 170° (77°C) which has received the 
name of acetonitrile C 4 H 3 N. When boiled with acids or alkalis it re-assimi- 
lates the 4 eq. of water, being converted again into acetic acid and ammonia. 
This substance is the type of a class ; great many ammonia-salts of acids, 
analagous to acetic acid, undergoing a similar change when treated with an- 
hydrous phosphoric acid. It is likewise obtained by a perfectly different 
process, which will be described when treating of the methyl-compounds. 
(See cyanide of methyl, page 383, and also acetic ether, page 356.) 

The acetates of lime, baryta, and strontia are very soluble, and can be pro- 
cured in crystals ; acetate of magnesia crystallizes with difficulty. 

Acetate of alumina, A1 2 3 ,3C 4 H 3 3 . — This salt is very soluble in water, 
and dries up in the vacuum of the air-pump to a gummy mass, without trace 

1 Acetic acid increases in density by the addition of water, and reaches its maximum 1.079 
when 30 parts have been mixed with 100 of the strongest acid; it then decreases in densit\, 
and when 135 parts have been added its specific gravity is the same as the hydrate, 1.063° 
The most ready method to test its strength is to suspend in it a fragment of pure marble of 
known weight; the loss of weight resulting will be five-sixths of the weight of the hydrated 
acid present, 50 parts of carbonate of lime being required to saturate 60 parts of acetk 
acid.— R. B. 
89 



374 ACETIC ACID. 

of crystallization. If foreign salts be present, the solution of the acetate 
becomes turbid on heating, from the separation of a basic compound, -which 
re-dissolves as the liquid cools. Acetate of alumina is much employed in 
calico-printing; it is prepared by mixing solutions of acetate of lead and 
alum, and filtering from the insoluble sulphate of lead. The liquid is thick- 
ened with gum or other suitable material, and with it the design is impressed 
upon the cloth by a wood-block, or by other means. Exposure to a moderate 
degree of heat drives off the acetic acid,«and leaves the alumina in a state 
capable of entering into combination with the dye-stuff. 

Acetate of manganese forms colourless, rhombic, prismatic crystals, perma- 
nent in the air. Acetate of protoxide of iron crj^stallizes in small greenish- 
white needles, very prone to oxidation ; both salts dissolve freely in water. 
Acetate of sesquioxide of iron is a dark-brownish red, uncrystallizable liquid, 
of powerful astringent taste. Acetate of cobalt forms a violet-coloured, crys- 
talline, deliquescent mass. The nickel-salt separates in green crystals, which 
dissolve in 6 parts of water. 

Acetate op lead, PbO, C 4 H 3 3 -J-3HO. — This important salt is prepared 
on a large scale by dissolving litharge in acetic acid ; it may be obtained in 
colourless, transparent, prismatic crystals, but is generally met with in com- 
merce as a confusedly crystalline mass, somewhat resembling loaf-sugar. 
From this circumstance, and from its sweet taste, it is often called sugar of 
lead. The crystals are soluble in about 1} parts of cold water, effloresce in 
dry air, and melt when gently heated in their water of crystallization ; the 
latter is easily driven off, and the anhydrous salt obtained, which suffers the 
igneous fusion, and afterwards decomposes, at a high temperature. Acetate 
of lead is soluble in alcohol. The watery solution has an intensely sweet, 
and at the same time astringent, taste, and is not precipitated by ammonia. 
It is an article of great value to the chemist. 

Basic acetates (subacetates) op lead. — Sesgui-basic acetate is produced 
when the neutral anhydrous salt is so far decomposed by heat as to become 
converted into a porous white mass, decomposable only at a much higher 
temperature. It is soluble in water, and separates from the solution evapo- 
rated to a syrupy consistence in the form of crystalline scales. It contains 
3PbO,2C 4 H 3 3 . A sub-acetate with 3 eq. of base is obtained by digesting at 
a moderate heat 7 parts of finely-powdered litharge, 6 parts of acetate of 
lead, and 30 parts of water. Or, by mixing a cold saturated solution of neu- 
tral acetate with a fifth of its volume of caustic ammonia, and leaving the 
whole some time in a covered vessel; the salt separates in minute needles, 
which contain 3PbO,C 4 H 3 3 -}-HO. The solution of sub-acetate prepared by 
the first method is known in pharmacy under the name of Goulard water. 
A third sub-acetate exists, formed by adding a great excess of ammonia to a 
solution of acetate of lead, or by digesting acetate of lead with a large quan- 
tity of oxide. It is a white, slightly crystalline substance, insoluble in cold, 
and but little soluble in boiling water. It contains 6PbO,C 4 H 3 3 . The solu- 
tions of the sub-acetates of lead have a strong alkaline reaction, and absorb 
carbonic acid with the greatest avidity, becoming turbid from the precipita 
tion of basic carbonate. 

Acetate op copper. — The neutral acetate, CuO,C 4 H 3 3 -f-HO, is prepared 
by dissolving verdigris in hot acetic acid, and leaving the filtered solution to 
cool. It forms beautiful dark-green crystals, which dissolve in 14 parts of 
cold and 5 parts of boiling water, and are also soluble in alcohol. A solution 
of this salt, mixed with sugar and heated, yields suboxide of copper in the 
form of minute red octahedral crystals; the residual copper solution is not 
precipitated by an alkali. Acetate of copper furnishes, by destructive distil 
lation, strong acetic acid, containing acetone, and contaminated with copper. 
The salt i» sometimes called distilled verdigris, and is used as a pigment. 



CHLORACETIC ACID. 375 

Basic acetates (sub-acetates) of copper. — Common verdigris, made 
by spreading the marc of grapes upon plates of copper exposed to the air 
during several weeks, or by substituting, with the same view, pieces of cloth 
dipped in crude acetic acid, is a mixture of several basic acetates of copper 
which have a green or blue colour. One of these, 3CuO,2C 4 H 3 3 -f-6HO, is 
obtained by digesting the powdered verdigris in warm water, and leaving the 
soluble part to spontaneous evaporation. It forms a blue, crystalline mass, 
but little soluble in cold water. AVhen boiled, it deposits a brown powder, 
which is a sub-salt with large excess of base. The green insoluble residue 
of the verdigris contains 3CuO,C 4 H 3 3 -{-3HO : it may be formed by digesting 
neutral acetate of copper with the hydrated oxide. By ebullition with water 
it is resolved into neutral acetate and the brown sub-salt. 

Acetate of silver, AgO,C 4 H 3 3 , is obtained by mixing acetate of potassa 
with nitrate of silver, and washing the precipitate with cold water to remove 
the nitrate of potassa. It crystallizes from a warm solution in small colour- 
less needles, which have but little solubility in the cold. 

Acetate of suboxide of mercury forms small scaly crystals, which are as feebly 
soluble as those of acetate of silver. The salt of the red oxide of mercury dis- 
solves with facility. 

Chloracetic acid. — "When a small quantity of crystallizable acetic acid 
is introduced into a bottle of dry chlorine gas, and the whole exposed to the 
direct solar rays for several hours, the interior of the vessel is found coated 
with a white crystalline substance, which is a mixture of the new product, 
the chloracetic acid, with a small quantity of oxalic acid. The liquid at the 
bottom contains the same substances, together with the unaltered acetic acid. 
Hydrochloric and carbonic acid gases are at the same time produced, together 
with suffocating vapour, resembling chloro-carbonic acid. The crystalline 
matter is dissolved out with a small quantity of water, added to the liquid 
contained in the bottle, and the whole placed in the vacuum of the air-pump, 
with capsules containing fragments of caustic potassa, and concentrated sul- 
phuric acid. The oxalic acid is first deposited, and afterwards the new sub- 
stance in beautiful rhombic crystals. If the liquid refuses to crystallize, it 
may be distilled with a little anhydrous phosphoric acid, and then evaporated. 
The crystals are spread upon bibulous paper to drain, and dried in vacuo. 

Chloracetic acid is a colourless and extremely deliquescent substance; it 
has a faint odour, and a sharp, caustic taste, bleaching the tongue and 
destroying the skin; the solution is powerfully acid. At 115° (46°C) it 
melts to a clear liquid, and at 390° (218°-8C) boils and distils unchanged. 
The density of the fused acid is 1-617 ; that of the vapour, which is very irri- 
tating, is probably 5-6. The substance contains, according to the analysis 
of M. Dumas, C 4 C1 3 3 ,H0, or the elements of hydrated acetic acid from 
which 3 eq. of hydrogen have been withdrawn, and 3 eq. of chlorine substi- 
tuted. 

Chloracetic acid forms a variety of salts, which have been examined and 
described ; it combines also with ether, and with the ether of wood-spirit. 
These compounds correspond to the ethers of the other organic acid. Chlora- 
cetate of potassa crystallizes in fibrous, silky needles, which are permanent 
in the air, and contain KO,C 4 Cl 3 3 -f-HO. The ammoniacal salt is also crys- 
tallizable and neutral ; it contains NJi 4 0,C 4 Cl 3 3 -}-5HO. Chloracelate ofsilca 
is a soluble compound, crystallizing in small greyish scales, which are easily 
altered by light; it gives, on analysis, AgO,C 4 C] 3 3 , and is consequently 
anhydrous. 

"When chloracetic acid is boiled with an excess of ammonia, it is decom> 
posed, with production of chloroform and carbonate of ammonia. 

C 4 H C1 3 4 =C 2 H Cl 3 and C 2 4 . 



376 ACETONE. 

With caustic potassa, it yields a smaller quantity of chloroform, chloride 
of potassium, carbonate and formate of potassa. The chloride and the for- 
mate are secondary products of the reaction of the alkali upon the chloro- 
form. 

Normal acetic may be reproduced from this curious substitution-compound. 
When an amalgam of potassium and mercury is put into a strong aqueous 
solution of chloracetic acid, chemical action ensues, the temparature of the. 
liquid rises, without disengagement of gas, and the solution is found to con- 
tain acetate of potassa, chloride of potassium, and some caustic potassa. 

Acetone ; pyroacetic spirit. — When metallic acetates in an anhydrous 
state are subjected to destructive distillation, they yield, among other pro- 
ducts, a peculiar inflammable, volatile liquid, designated by the above names. 
It is most easily prepared by distilling carefully dried acetate of lead in a 
large earthen or coated glass retort, by a heat gradually raised to redness; 
the retort must be connected with a condenser well supplied with cold water. 
Much gas is evolved, chiefly carbonic acid, and the volatile product, but 
slightly contaminated with tar, collects in the receiver. The retort is found 
after the operation to contain minutely divided metallic lead, which is some- 
times pyrophoric. The crude acetone is saturated with carbonate of po- 
tassa, and afterwards rectified in a water-bath from chloride of calcium. 
This compound may also be prepared by passing the vapour of strong acetic 
acid through an Jron tube heated to dull redness ; the acid is resolved into 
acetone, carbonic acid, carbonic oxide, and carbonetted hydrogen. 

Pure acetone is a colourless limpid liquid, of peculiar odour; it has a 
density of 0-792, and boils at 132° (55°-5C) ; the density of its vapour, 
2 022. Acetone is very inflammable, and burns with a bright flame; it is 
miscible in all proportions with water, alcohol, and ether. The simplest 
formula of this substance which is produced by the resolution of acetic acid 
into acetone and carbonic acid, is C 3 H 3 ; but it is probable that this for- 
mula should be doubled. 

When acetone is distilled with half its volume of Nordhausen sulphuric 
acid, an oily liquid is obtained, which in a state of purity has a feeble garlic 
odour. It is lighter than water, and very inflammable. It contains Ci 8 H, 2 , 
and is produced by the abstraction of the elements of water from acetone. 
It has received the name mesitilole. If pentachloride of phosphorus be 
dropped into carefully cooled acetone, and the whole mixed with water, a 
heavy oily liquid separates, which is stated to contain C 6 H 5 C1. When this 
is dissolved in alcohol, and mixed with caustic potassa, a second oily pro- 
duct results. This is lighter than water, has an aromatic odour, and con- 
tains C 6 H 6 0. 

Sir Robert Kane has described a number of other compounds formed by 
the action of acids, and other chemical agents, on acetone, from which he 
has inferred the existence of an organic salt-basyle, containing C 6 H 5 , and to 
which the name of mesityl has been given. Zeise, on the other hand, has 
shown that by the action of chloride of platinum upon acetone, a yellow 
crystallizable compound can be obtained, having a composition expressed by 
the formula C 6 H 5 0-f-PtCl 2 . 

Acetic acid is not the only source of acetone ; it is produced in the de- 
structive distillation of citric acid, and may be procured from sugar, starch, 
and gum by distillation with 8 times their weight of powdered quick-lime 
The acetone is, in this case, accompanied by an oily, volatile liquid, sepa- 
rable by water, in which it is insoluble. This substance is called metacetone 
or propione ; it contains C 5 H 5 0, its boiling-point is 212° (100°C). 

Propionic acid. — Metacetone distilled with a mixture of bichromate of 
potassa and sulphuric acid yields, among other products, metacetonic or pro- 
pionic acid C s H 5 3 ,HO, a volatile acid, very closely resembling acetic acid, 



KAKODYL AND ITS COMPOUNDS. 377 

and chiefly distinguished from that substance by the high degree of solu- 
bility of its soda-salt. Mr. Morley has lately shown that propionate of ba- 
ryta when submitted to destructive distillation, yields again propione. Pro- 
pionic acid is one of the products of the action of hydrate of potassa in a 
melted state upon sugar, and is also generated by the fermentation of gly- 
cerin. The formation of this substance by the action of potassa upon cy- 
anide of ethyl has been already mentioned, page 354. 

When acetate of potassa is heated with a great excess of caustic alkali it 
is converted, as already remarked, 1 into carbonic acid and light carbonetted 
hydrogen, by the reaction of the oxygen of the water of the hydrate upon 
the carbon of the acid. 

C 4 H 3 3 ,HO=C 2 4 -{-C 2 rI 4 . 



KAKODYL AND ITS COMPOUNDS. 



The substance long known under the name of fuming liquor of Cadet, pre- 
pared by distilling a mixture of dry acetate of potassa and arsenious acid, 
has been shown by M. Bunsen to be the oxide of an isolable organic basyl, 
capable of forming a vast number of combinations, displacing other bodies, 
and being in turn displaced by them, in the same manner as a metal. The 
investigation of this difficult subject reflects the highest honour .on the pa- 
tience and skill of the discoverer. Kakodyl, so named from its poisonous 
and offensive nature, contains three elements, viz., carbon, hydrogen, and 
arsenic. 

Table of the most important Kalcodyl- Compounds. 

Kakodyl (symbol Kd) C 4 H 6 As. 

Oxide of kakodyl KdO. 

Chloride of kakodyl KdCl. 

Chloride of kakodyl and copper KdCl-f-Cu 2 Cl. 

Oxy-chloride of kakodyl 3KdCl-}-KdO. 

Terchloride of kakodyl KdCl 3 . 

Bromide of kakodyl KdBr. 

Iodide of kakodyl Kdl. 

Cyanide of kakodyl KdCy. 

Kakodylic acid Kd0 3 . 

Kakodylate of silver AgO,Kd0 3 . 

Kakodylate of kakodyl KdO,Kd0 3 . 

Sulphide ofkakodyl KdS. 

Sulphide ofkakodyl and copper KdS-f-3CuS. 

Tersulphide ofkakodyl KdS 3 . 

Sulphur-salts containing tersulphide \ KdS,KdS 3 — AuS,KdS 3 . 

ofkakodyl / CuS,KdS 3 — PbS,KdS a . 

Selenide ofkakodyl KdSe. 

Oxide of kakodyl; Cadet's fuming liquid ; alkarsin ; KdO. — Equal 
weights of acetate of potassa and arsenious acid are intimately mixed, and 
introduced into a glass retort connected with a condenser and tubulated re- 
ceiver, cooled by ice : a glass tube is attached to the receiver to carry away 
the permanently-gaseous products to some distance from the experimenter. 

1 See page 153. 
32* 



378 KAKODYL AND ITS COMPOUNDS. 

Heat is then applied to the retort, which is gradually increased to redness. 
At the close of the operation, the receiver is found to contain two liquids, 
besides a quantity of reduced arsenic : the heavier of these is the oxide of 
kakodyl in a coloured and impure condition ; the other chiefly consists of 
water, acetic acid, and acetone. The gas given off during distillation is 
principally carbonic acid. The crude oxide of kakodyl is repeatedly washed 
by agitation with water, previously freed from air by boiling, and afterwards 
re-distilled from hydrate of potassa in a vessel filled with pure hydrogen gas. 
All these operations must be conducted in the open air, and the strictest pre- 
cautions adopted to avoid the accidental inhalation of the smallest quantity 
of the vapour or its products. 

Oxide of kakodyl is a colourless, ethereal liquid of great refractive power ; 
it is much heavier than water, having a density of 1-462. It is very slightly 
soluble in water, but easily dissolved by alcohol ; its boiling-point approaches 
302° (150°C), and it solidifies to a white crystalline mass at 9° ( — 12°-6C). 
The odour of this substance is extremely offensive, resembling that of arse- 
netted hydrogen : the minutest quantity attacks the eyes and the mucous 
membrane of the nose ; a larger dose is highly dangerous. When exposed 
to the air, oxide of kakodyl emits a dense white smoke, becomes heated, and 
eventually takes fire, burning with a pale flame, and producing carbonic acid, 
water, and a copious cloud of arsenious acid. It explodes when brought into 
contact with strong nitric acid, and inflames spontaneously when thrown into 
chlorine gas. The density of the vapour of this body is about 7*5. Oxide 
of kakodyl is generated by the reaction of arsenious acid on the elements of 
acetone, cai-bonic acid being at the same time formed ; the accompanying 
products are accidental : — 

2 eq. acetone C 6 H 6 2 , and 1 eq. arsenious acid, As0 3 =l eq. oxide kakodyl, 
C 4 H 6 AsO, and 2 eq. carbonic acid, C 2 4 . 

Chloride of Kakodyl, KdCl. — A dilute alcoholic solution of oxide of 
kakodyl is cautiously mixed with an equally dilute solution of corrosive 
sublimate, avoiding an excess of the latter ; a white, crystalline, inodorous 
precipitate falls, containing Kd0-f-2HgCl; when this is distilled with con- 
centrated liquid hydrochloric acid, it yields corrosive sublimate, water, and 
chloride of kakodyl, which distils over. The product is left some time in 
contact with chloride of calcium and a little quicklime, and then distilled 
alone in an atmosphere of carbonic acid. The pure chloride is a colourless 
liquid, which does not fume in the air, but emits a vapour even more fearful 
in its effects, and more insupportable in odour than that of the oxide. It is 
heavier than water, and insoluble in that liquid, as also in ether; alcohol, on 
the other hand, dissolves it with facility. The boiling-point of this compound 
is a little above 212° (100°C) ; its vapour is colourless, is spontaneously in- 
flammable in the air, and has a density of 4-56. Dilute nitric acid dissolves 
the chloride without change; with the concentrated acid ignition and explo- 
sion occur. Chloride of kakodyl combines with subchloride of copper to a 
white, insoluble, crystalline double salt, containing KdCl-j-Cu 2 Cl, and also 
with oxide of kakodyl. 

Kakodyl, in a free state, may be obtained by the action of metallic 
zinc, iron, or tin upon the above-described compound. Pure and anhydrous 
chloride of kakodyl is digested for three hours, at a temperr ture of 212° 
|dOO°C), with slips of clean metallic zinc contained in a bulb blown upon a 
glass tube, previously filled with carbonic acid gas, and hermetically sealed. 
The metal dissolves quietly without evolution of gas. "When the action ia 
complete, and the whole cool, the vessel is observed to contain a white saline 
mass, which on the admission of a little water dissolves, and liberates a 
heavy oily liquid, the kakodyl itself. This is rendered quite pure by distil- 
lation from a fresh quantity of zinc, the process being conducted in the little 




KAKODYL AND ITS COMPOUNDS. 379 

apparatus shown in the margin (fig. 170), which is made Fig. 170. 

from a piece of glass tube, and is intended to serve the pur- 
pose both of retort and receiver. The zinc is introduced 
into the upper bulb, and then the tube drawn out in the 
manner represented. The whole is then filled with carbonic 
acid, and the lower extremity put into communication with 
a little hand-syringe. On dipping the point a into the crude 
kakodyl and making a slight movement of exhaustion, the 
liquid is drawn up into the bulb. Both extremities are 
then sealed in the blow-pipe flame, and after a short diges- 
tion at 212° (100°C) or a little above, the pure kakodyl is 
distilled off into the lower bulb, which is kept cool. It 
forms a colourless, transparent, thin liquid, much resemb- 
ling the oxide in odour, and surpassing that substance in 
inflammability. When poured into the air, or into oxygen 
gas, it ignites instantly ; the same thing happens with chlo- 
rine. With very limited access of air it throws off white fumes, passing into 
oxide, and eventually into kakodylic acid. Kakodyl boils at 838° (170°C), 
and when cooled to 21° ( — 6°-lC) crystallizes in large, transparent, square 
prisms. It, combines directly with sulphur and chlorine, and in fact may 
readily be made to furnish all the compounds previously derived from the 
oxide. It constitutes the most perfect type of an organic quasi-metal which 
chemistry yet possesses. 

Kakodyl is decomposed by a temperature inferior to redness into metallic 
arsenic, and a mixture of 2 measures light carbonetted hydrogen, and 1 
measure defiant gas. 

Chloride of kakodyl forms a hydrate, which is thick and viscid, and readily 
decomposable by chloride of calcium, which withdraws the water. In the 
preparation of the chloride, and also in other operations, a small quantity of 
a red amorphous powder is often obtained, called erytrarsin. This is inso- 
luble in water, alcohol, ether, and caustic potassa, but is gradually oxidized 
by exposure to the air, with production of arsenious acid. It contains 
C 4 H 6 3 As 3 . 

Iodide of kakodyl, Kdl. — This is a thin, yellowish liquid, of offensive 
odour, and considerable specific gravity, prepared by distilling oxide of 
kakodyl with strong solution of hydriodic acid. A yellow crystalline sub- 
stance is at the same time formed, which is an oxy-iodide. Bromide and 
fluoride of kakodyl have likewise been obtained and examined. 

Sulphide of kakodyl, KdS, is prepared by distilling chloride of kakodyl 
with a solution of the bisulphide of barium and hydrogen. It is a clear, thin, 
colourless liquid, smelling at once of alkarsin and mercaptan, insoluble in 
water, and spontaneously inflammable in the air. Its boiling-point is high, 
but it distils easily with the vapour of water. This substance dissolves 
sulphur, and generates tersulphide of kakodyl, KdS* 3 , which is a sulphur- 
acid, and combines with the sulphides of gold, copper, bismuth, lead, and 
antimony. 

Cya>-ide of kakodyl, KdCy. — The cyanide is easily formed by distilling 
alkarsin with strong hydrocyanic acid, or cyanide of mercury. Above 91 ° 
(32° -7C) it is a colourless, ethereal liquid, but below that temperature it 
crystallizes in colourless, four-sided prisms, of beautiful diamond lustre. It 
boils at about 284° (140°C), and is but slightly soluble in water. It requires 
to be heated before inflammation occurs. The vapour of this substance is 
most fearfully poisonous ; the atmosphere of a room is said to be so far con- 
taminated by the evaporation of a few grains, as to cause instantaneous 
numbness of the hands and feet, vertigo, and even unconsciousness. 

Kakodylic acid (alkaegen) ; Kd0 3 . — This is the ultimate product of the 



880 KAKODYL AND ITS COMPOUNDS. 

action of oxygen at a low temperature upon kakodyl or its oxide ; it is best 
prepared by adding oxide of mercury to that substance, covered with a layer 
of water, and artificially cooled, until the mixture loses all odour, and after- 
wards decomposing any kakodylate of mercury, that may have been formed, 
by the cautious addition of more alkarsin. The liquid furnishes, by evapo- 
ration to dryness and solution in alcohol, crystals of the new acid. The 
sulphide, and other compounds of kakoclyl, yield, by exposure to air, the 
same substance. Kakodylic acid forms brilliant, colourless, brittle crystals, 
which have the form of a modified square prism ; it is permanent in dry air, 
but deliquescent in a moist atmosphere. It is very soluble in water and in 
alcohol, but not in ether ; the solution has an acid reaction. When mixed 
with alkalis and evaporated, a gummy, amorphous mass results. With the 
oxides of silver and mercury, on the other hand, it yields crystallizable com- 
pounds. It unites with oxide of kakodyl, and forms a variety of combinations 
with metallic salts. Alkargen is exceedingly stable ; it is neither affected by 
red, fuming nitric acid, aqua regia, nor even chromic acid in solution ; it 
may be boiled with these substances without the least change. It is deoxi- 
dized, however, by phosphorous acid and protochloride of tin to oxide of 
kakodyl. Dry hydriodic acid gas decomposes it, with production of water, 
iodide of kakodyl, and free iodine ; hydrochloric acid, under similar circum- 
stances, converts it into a corresponding terchloinde, which is solid and crys- 
tallizable. Lastly, what is extremely remarkable, this substance is not in 
the least degree poisonous. 

Parakakodylic oxide. — When air is allowed access to a quantity of 
alkarsin, so slowly that no sensible rise of temperature follows, that body is 
gradually converted into a thick syrupy liquid, full of crystals of kakodylic 
acid. Long exposure to air, or the passage of a copious current through the 
mass, heated to 158° (70°C), fails to induce crystallization of the whole. If 
in this state water be added, everything dissolves, and a solution results 
which contains kakodylic acid, partly free, and partly in combination with 
the oxide of kakodyl. When this liquid is distilled, water, having the odour 
of alkarsin, passes over, and afterwards an oily liquid, which is the new 
compound. Impure kakodylic acid remains in the retort. 

Parakakodylic oxide, purified by rectification from caustic baryta, is a 
colourless, oily liquid, strongly resembling alkarsin itself in odour, relations 
to solvents, and in the great number of its reactions. It neither fumes in 
the air, however, nor takes fire at common temperatures ; its vapour, mixed 
with air, and heated to 190° (87° -8C), explodes with violence. By analysis, 
't is found to have exactly the same composition as ordinary oxide of kakod\l. 



WOOD-SPIRIT AND ITS DERIVATIVES. 381 



SECTION II. 
SUBSTANCES MORE OR LESS ALLIED TO ALCOHOL. 



WOOD-SPIRIT AND ITS DERIVATIVES. 

In the year 1812, Mr. P. Taylor discovered, among the liquid products 
of the destructive distillation of dry-wood, a peculiar volatile inflammable 
liquid, much resembling spirit of wine, to which allusion has already been 
made. This substance has been shown by MM. Dumas and Peligot to be 
really a second alcohol, forming an ether, and a series of compounds, exactly 
corresponding with those of vinous spirit, and even more complete, in some 
points, than the latter. Wood-spirit, like ordinary alcohol, may be regarded 
as a hydrated oxide of a body like ethyl, containing C 2 H 3 , called methyl. 1 

A very great number of compound methyl-ethers have been described; 
they present the most complete parallelism of origin, properties, and consti- 
tution with those derived from common alcohol. 

Wood-spirit Series. 

Methyl (symbol, Me) C 2 H 2 

Oxide of methyl C 2 H 3 

Hydride of methyl (marsh gas) C 2 H 3 H 

Chloride of methyl C 2 H 3 C1 

Iodide of methyl &c C 2 H 3 I 

Zinc-methyl C 2 H 3 Zn 

Wood-spirit C 2 H 3 0,HO 

Sulphate of oxide of methyl C 2 H 3 0,S0 3 

Nitrate of oxide of methyl &c C 2 H 3 0,N0 5 

Sulphomethylic acid C 2 H 3 0,2S0 3 ,H0 

Formic acid C 2 H 3 ,H0 

Chloroform C 2 H Cl 8 

Hydrated oxide oe methyl ; pyroxylic spirit ; wood-spirit ; MeO,HO 
— The crude wood-vinegar probably contains about —L part of this sub 
stance, which is separated from the great bulk of the liquid by subjecting 
the whole to distillation, and collecting apart the first portions which pass 
over. The acid solution thus obtained is neutralized by hydrate of lime, the 
clear liquid separated from the oil which floats on the surface, and from thy 
sediment at the bottom of the vessel, and again distilled. A volatile liquid, 
which burns like weak alcohol, is obtained ; this may be strengthened in the 
same manner as ordinary spirit, by rectification, and ultimately rendered 
pure and anhydrous, by careful distillation from quick-lime by the heat of a 
water-bath. Pure wood-spirit is a colourless, thin liquid, of peculiar odour, 
quite different from that of alcohol, and burning, disagreeable taste ; it boils 

1 From fiiOv, wine, and v\rj, wood ; the termination vXrj, or yl, is very frequently 
employed in the s?ns"> of matter, material. 



382 WOOD-SPIRIT AND ITS DERIVATIVES. 

at 152° (66° -6C), and has a density of 0-798 at 68° (20C). The dsnsity of 
its vapour is 1-12. Wood-spirit mixes in all proportions with water, when 
pure ; it dissolves resins and volatile oils as freely as alcohol, and is often 
substituted for alcohol in various processes in the arts, for which purpose it 
is prepared on a large scale. It may be burned instead of ordinary spirit, 
in lamps ; the flame is pale-coloured, like that of alcohol, and deposits no 
soot. Wood-spirit dissolves caustic baryta ; the solution deposits, by evapo- 
ration in vacuo, acicular crystals, containing BaO-f-MeO,HO. Like alcohol, 
it dissolves chloride of calcium in large quantity, and gives rise to a crystal- 
line compound, resembling that formed by alcohol, and containing, according 
to Kane, CaCl-f 2(MeO,HO). 

Oxide op methyl ; wood-ether ; MeO. — One part of wood-spirit and 4 
parts of concentrated sulphuric acid are mixed and exposed to heat in a 
flask fitted with a perforated cork and bent tube ; the liquid slowly blackens, 
and emits large quantities of gas, which may be passed through a little 
strong solution of caustic potassa, and collected over mercury. This is the 
zvood-spirit ether, a permanently gaseous substance, which does not liquefy at 
the temperature of 3° ( — 16°-1C). It is colourless, has an ethereal odour, 
and burns with a pale and feebly luminous flame. Its specific gravity is 
1-617. Cold water dissolves about 36 times its volume of this gas, acquiring 
thereby the characteristic taste and odour of the substance ; when boiled, 
the gas is again liberated. Alcohol, wood-spirit, and concentrated sulphuric 
acid, dissolve it in still larger quantity. 

Under the head of ether it has been mentioned that the generally received 
relation of this substance to the other ethyl-compounds had been rendered 
doubtful by recent researches. The same remark of course applies to me- 
thylic ether, which is in every respect analogous to common ethers. It was 
first proposed by Berzelius, and has long been urged by MM. Laurent and 
Gerhardt, that the composition of alcohol being expressed by the formula 
C 4 H 6 2 , the true formula of ether was C 8 H ]0 O 2 , and not C 4 H 5 0. The cor- 
rectness of this view has lately been established by a series of beautiful ex- 
periments carried out by Prof. Williamson. He found that the substance 
produced by dissolving potassium in alcohol, which has the formula C 4 H 5 0, 
KO, when acted upon by iodide of ethyl, furnishes iodide of potassium and 
perfectly pure ether. This reaction may be expressed by the two following 
equations : — 

C 4 H 5 0,KO + C 4 H 5 I = KI -f 2C 4 H 5 0, or 
C 4 H 5 0,KO -f- C 4 II 5 I = KI -f C 8 H 10 O 2 . 

That in this reaction, not two equivalents of ether, as represented in the 
first equation, but a compound C s H, O 2 is formed, as expressed in the second, 
is clearly proved by substituting, when acting upon the compound C 4 H 5 0,KO, 
for the iodide of ethyl, the corresponding methyl-compound. In this case 
neither common ether nor methyl-ether is formed, but an intermediate com- 
pound C 6 H 8 2 = C 4 H 5 0,C 2 H 3 0. This substance is insoluble in water, and 
has a peculiar odour similar to that of ether, but boils at 50° (10°C). 

It is very probable that the substances, which have been described by 
the terms ethyl and methyl, likewise are not C 4 H 5 and C 2 H 3 , but C g H 10 and 
C 4 H 6 . The limits of this elementary work will not permit us to enter into 
the details of this question, which is still under the discussion of scientific 
chemists. 

Chloride of methyl, MeCl. — This compound is most easily prepared by 
heating a mixture of 2 parts of common salt, 1 of wood-spirit, and 3 of con- 
centrated sulphuric acid ; it is a gaseous body, which may be conveniently 
collected over water, as it is but slightly soluble in that liquid. Chloride of 
methyl is colourless; it has a peculiar odour and sweetish taste, and burns. 



WOOD-SPIRIT AND ITS DERIVATIVES. 883 

when kindled, -with a pale flame, greenish towards the edges, like most com- 
bustible chlorine-compounds. It has a density of 1-731, and is not liquefied 
at 0° ( — 17°-7C). The gas is decomposed by transmission through a red-hot 
tube, with slight deposition of carbon, into hydrochloric acid gas and a car- 
bonetted hydrogen, which has been but little examined. 

Iodide op methyl, Mel, is a colourless and feebly combustible liquid, 
obtained by distilling together 1 part of phosphorus, 8 of iodine, and 12 or 
15 of wood-spirit. It is insoluble in water, has a density of 2-257, and 
boils at 111° (43°-8C). The density of its vapour is 4-883. The action of 
zinc upon iodide of methyl in sealed tubes furnishes a colourless gas, appa- 
rently a mixture of several substances, among which methyl may occur. 1 
The residue contains iodide of zinc together with a volatile substance of very 
disagreeable odour, which absorbs oxygen with so much avidity, that it takes 
fire when coming in contact with the air. It is zinc-m'ethyl, C 4 H 5 Zn, cor- 
responding to zinc-ethyl. (See page 368.) When mixed with water it yields 
oxide of zinc and light carbonetted hydrogen. 

Cyanide of methyl, MeCy. — If a dry mixture of sulphomethylate of 
baryta and cyanide of potassium are heated in a retort, a very volatile liquid 
of a powerful odour distils over. It generally contains hydrocyanic acid and 
water, from which it is separated by distillation, first over red oxide of mer- 
cury, and then over anhydrous phosphoric acid. When thus purified, it has 
an agreeable aromatic odour, and boils at 170°-6 (77°C). When boiled with 
potassa, it undergoes a decomposition analogous to that of cyanide of ethyl, 
(see page 354)'; it absorbs 4 eq. of water, and yields acetic acid and am- 
nionia. 

MeCy = C 4 H 3 N I 



C 4 H 7 N0 4 | C 4 H 7 N0 4 

It has been mentioned that this compound may be obtained by abstracting 
4 eq. of water from acetate of ammonia by means of phosphoric acid. (See 
(page 373.) 

Compounds of methyl with bromine, fluorine, and sulphur have also been 
obtained. 

Sulphate op oxide of methyl, MeO,S0 3 . — This interesting substance is 
prepared by distilling 1 part of wood-spirit with 8 or 10 of strong oil of 
vitriol : the distillation may be carried nearly to dryness. The oleaginous 
liquid found in the receiver is agitated with water, and purified by rectifica- 
tion from powdered caustic baryta. The product, which is the body sought, 
is a colourless oily liquid, of alliaceous odour, having a density of 1-324, and 
boiling at 370° (187°7C). It is neutral to test-paper, and insoluble in water, 
but decomposed by that liquid, slowly in the cold, rapidly and with violence 
at a boiling temperature, into sulphomethylic acid and wood-spirit, which is 
thus reproduced by hydration of the liberated methylic ether. Anhydrous 
lime or baryta have no action on this summit ; their hydrates, however, and 
those of potassa and soda, decompose it instantly, with production of a sul : 
phomethylate of the base, and wood-spirit. When neutral sulphate of methyl 
is heated with common salt, it yields sulphate of soda and chloride of methyl ; 
with cyanide of mercury or potassium, it gives a sulphate of the base, and 
cyanide of methyl ; with dry formate of soda, sulphate of soda and formate 
of methyl. These reactions possess great interest. 

1 The same compound is believed to occur among the substances produced by the action of 
a galvanic current upon acetic acid. See valerianic acid, page 392. 



384 WOOD-SPIRIT AND ITS DERIVATIVES. 

Nitrate of oxide of methyl, MeO,N0 5 . — One part of nitrate of 
potassa is introduced into a retort, connected with a tubulated receiver, to 
which is attached a bottle, containing salt and water, cooled by a freezing, 
mixture ; a second tube serves to carry off the incondensible gases to a chim- 
ney. A mixture of one part of wood-spirit and 2 of oil of vitriol is made, and 
immediately poured upon the nitre ; reaction commences at once, and requires 
but little aid from external heat. A small quantity of red vapour is seen to 
arise, and an ethereal liquid condenses, in great abundance, in the receiver, 
and also in the bottle. When the process is at an end, the distilled products 
are mixed, and the heavy oily liquid obtained separated from the water. It 
is purified by several successive distillations by the heat of a water-bath from 
a mixture of chloride of calcium and litharge, and, lastly, rectified alone in a 
retort, furnished with a thermometer passing through the tabulature. The 
liquor begins to boil at about 140° (60°C) ; the temperature soon rises to 
150° (65° -5C), at which point it remains constant ; the product is then col- 
lected apart, the first and most volatile portions being contaminated with 
hydrocyanic acid and other impurities. Even with these precautions, the 
nitrate of methyl is not quite pure, as the analytical results show. The pro- 
perties of the substance, however, remove any doubts respecting its real 
nature. 

Nitrate of methyl is colourless, neutral, and of feeble odour ; its density is 
1-182; it boils at 150° (65°-5C), and burns, when kindled, with a yellow 
flame. Its vapour has a density of 2-64, and is eminently explosive ; when 
heated in a flask or globe to 800° (140°C), or a little above, it explodes with 
fearful violence ; the determination of the density of the vapour is, conse- 
quently, an operation of danger. Nitrate of methyl is decomposed by a solu- 
tion of caustic potassa into nitrate of that base and wood-spirit. 

Oxalate of oxide of methyl, MeO, C 2 3 . — This beautiful and interest- 
ing substance is easily prepared by distilling a mixture of equal weights of 
oxalic acid, wood-spirit, and oil of vitriol. A spirituous liquid collects in the 
receiver, which, exposed to the air, quickly evaporates, leaving the oxalic 
methyl-ether in the form of rhombic transparent crystalline plates, which 
may be purified by pressure between folds of bibulous paper, and re-distilled 
from a litlle oxide of lead. The product is colourless, and has the odour of 
common oxalic ether; it melts at 124° (51°-1C), and boils at 322° (161 °C). 
It dissolves freely in alcohol and wood-spirit, and also in water, which, how- 
ever, rapidly decomposes it, especially when hot, into oxalic acid and. wood- 
spirit. The alkaline hydrates effect the same change even more easily. Solu- 
tion of ammonia converts it into oxanide and wood-spirit. "With dry ammo- 
niacal gas it yields a white, solid substance, which crystallizes from alcohol 
in pearly cubes ; this new body, designated oxamethylane, or oxamate of 
methyl, contains C 6 H 5 N0 6 =C 2 H 3 0,C 4 H 2 N0 5 . 

Many other salts of oxide of methyl have been formed and examined. The 
acetate, MeO,C 4 H 3 3 , is abundantly obtained by distilling 2 parts of wood- 
spirit with 1 of crystallizable acetic acid, and 1 of oil of vitriol. It much 
resembles acetic ether, having a density of 0-919, and boiling at 136°(57°-8C) ; ' 
the density of its vapour is 2-563. This compouud is isomeric with formic 
ether. Formate of methyl, Me0,C 2 H0 3 , is prepared by heating in a retort 
equal weights of sulphate of methyl and dry formate of soda, it is very vola- 
tile, lighter than water, and is isomeric with hydrate of acetic acid. Chloro- 
carbonic methyl-ether is produced by the action of that gas upon wood-spirit ; 
it is a colourless, thin, heavy, and very volatile liquid, containing C 4 H 3 C10 4 
= C 2 H 3 0,C 2 C10 3 . It yields with dry ammonia a solid crystallizable substunt 
called urethylane, C 4 II 5 N0 4 . (See page 358.) 

Sulphomethylic acid, MeO,2S0 8 ,HO. — Sulphomethylate of baryta is 
prepared in the same manner as the sulphovinate ; 1 part of wood-spirit is 



WOOD-SPIRIT AND ITS DERIVATIVES. 385 

eIowiv mixed with 2 parts of concentrated sulphuric acid, the whole heated 
to ebullition, and left to cool, after which it is diluted with water and neu- 
tralized with carbonate of baryta. The solution is filtered from the inso- 
luble sulphate, and evaporated, first in a water-bath, and afterwards in vacuo 
to the due degree of concentration. The salt ci^ystallizes in beautiful square 
colourless tables, containing BaO,C 2 H 3 0,2S0 3 -f-2HO, which effloresce in dry 
air, and are very soluble in water. By exactly precipitating the base from 
this substance by dilute sulphuric acid, and leaving the filtered liquid to eva- 
porate in the air, hydrated sulphomethylic acid may be procured in the form 
of a sour, syrupy liquid, or as minute acicular crystals, \ery soluble in 
water and alcohol. It is very instable, being decomposed by heat in the 
same manner as sulphovinic acid. Sulphomethylaie of potassa crystallizes in 
small, nacreous, rhombic tables, which are deliquescent; it contains KO, 
C 2 H 3 0,2S0 3 . The lead-salt is also very soluble. 

Formic acid. — As alcohol by oxidation under the influence of finely-divided 
platinum gives rise to acetic acid, so wood-spirit, under similar circumstan- 
ces, yields a peculiar acid product, produced by the substitution of 2 eq. of 
oxygen for 2 eq. of hydrogen, to which the term formic is given, from its oc- 
currence in the animal kingdom, in the bodies of ants. The experiment 
may be easily made by inclosing wood-spirit in a glass jar with a quantity 
of platinum-black, and allowing moderate excess of air; the spirit is gra- 
dually converted into formic acid. There has not been found an interme- 
diate product corresponding to aldehyde. Anhydrous formic acid, as in the 
salts, contains C 2 H0 3 , or the elements of 2 eq. carbonic oxide, and 1 eq. water. 

Pure hydrate formic acid, C 2 H0 3 ,HO, is obtained by the action of sulphu- 
retted hydrogen on dry formate of lead. The salt, reduced to fine powder, 
is very gently heated in a glass tube connected with a condensing apparatus, 
through which a current of dry sulphuretted hydrogen gas is transmitted. 
It forms a clear, colourless liquid, which fumes slightly in the air, of exceed- 
ingly penetrating odour, boiling at 209° (98°-5C), and crystallizing in large 
brilliant plates when cooled below 32° (0°C). The sp. gr. of the acid is 
1-235; it mixes with water in all proportions; the vapour is inflammable, 
and burns with a blue flame. A second hydrate, containing 2 eq. of water, 
exists; its density is I'll, and it boils at 223° (106°-1C). In its concen- 
trated form this acid is extremely corrosive; it attacks the skin, forming a 
blister or an ulcer, painful and difficult to heal. A more dilute acid may be 
prepared by a variety of processes : starch, sugar, and many other organic 
substances often yield formic acid when heated with oxidizing agents ; a con- 
venient method is the following : — 1 part of sugar, 3 of binoxide of manga- 
nese, and 2 of water, are mixed in a very capacious retort, or large metal 
still ; 3 parts of oil of vitriol, diluted with an equal weight of water, are 
then added, and when the first violent effervescence from the disengagement 
of carbonic acid has subsided, heat is cautiously applied, and a considerable 
quantity of liquid distilled over. This is very impure ; it contains a vola- 
tile oily matter, and some substance which communicates a pungency not 
proper to formic acid in that dilute state. The acid liquid is neutralized 
with carbonate of soda, and the resulting formate purified by crystallization, 
and if needful, by animal charcoal. From this, or any other of its salts, 
solution of formic acid may be readily obtained by distillation with dilute 
sulphuric acid. It has an odour and taste much resembling those of acetic 
acid, reddens litmus strongly, and decomposes the alkaline carbonates with 
effervescence. 

Another process for making formic acid consists in distilling dry oxalic 

acid, mixed with its own weight of sand or pumice- stone in a glass retort. 

Carbonic oxide and carbonic acid are disengaged, while a very acid liquid 

distils, which is formic acid contaminated with a small quantity of oxaJo 

33 



386 WOOD-SPIRIT AND ITS DERIVATIVES. 

add. By redistilling this mixture pure distilled formic acid is obtained. 
This process yields a very strong acid, but only a small quantity in pro- 
portion to the oxalic acid employed. 

Formic acid, in quantity, may be extracted from ants by distilling the 
insects with water, or by simply macerating them in the cold liquid. 

Formic acid is readily distinguished from acetic acid by heating it -with a 
little solution of oxide of silver or mercury; the metal is reduced, and pre- 
cipitated in a pulverulent state, while carbonic acid is extricated; this re- 
action is sufficiently intelligible. The protochloride of mercury is reduced, 
by the aid of the elements of water, to calomel, carbonic acid and hydro- 
chloric acids being formed. 

The most important salts of formic acid are the following : — Formate of 
soda crystallizes in rhombic prisms containing 2 eq. of water ; it is very so- 
luble, and is decomposed like the rest of the salts by hot oil of vitriol with 
evolution of pure carbonic oxide. Fused with many metallic oxides, it 
causes their reduction. Formate of potassa is with difficulty made to crys- 
tallize from its great solubility. Formate of ammonia crystallizes in square 
prisms ; it is very soluble, and is decomposed by a high temperature into 
hydrocyanic acid and water, the elements of which it contains, NH 4 0,C 2 H0 3 
— 4HO = C 2 NH. This decomposition is perfectly analogous to that of 
acetate of ammonia, see page 373. The salts of baryta, strontia, lime, and 
magnesia form small prismatic crystals, soluble without difficulty. Formate 
of lead crystallizes in small, diverging, colourless needles, which require for 
solution 40 parts of cold water. The formates of manganese, protoxide of 
iron, zinc, nickel, and cobalt, are also crystallizable. That of copper is very 
beautiful, constituting bright blue, rhombic prisms of considerable magni- 
tude. Formate of silver is white, but slightly soluble, and decomposed by 
the least elevation of temperature. 

Chloroform. — This substance is produced, as already remarked, when an 
aqueous solution of caustic alkali is made to act upon chloral. It may be 
obtained with greater facility by distilling alcohol, wood-spirit, or acetone 
with a solution of chloride of lime. 1 part of hydrate of lime is suspended 
in 24 parts of cold water, and chlorine passed through the mixture until 
nearly the whole lime is dissolved. A little more hydrate is then added to 
restore the alkaline reaction, the clear liquid mixed with 1 part of alcohol 
or wood-spirit, and, after an interval of 24 hours, cautiously distilled in a 
very spacious vessel. A watery liquid containing a little spirit and a heavy 
oil collect in the receiver; the latter, which is the chloroform, is agitated 
with water, digested with chloride of calcium, and rectified in a water-bath. 
It is a thin, colourless liquid of agreeable ethereal odour, much resembling 
that of Dutch-liquid, and sweetish taste. Its density is 1-48, and it boils at 
141°-8 (61°C) ; the density of its vapour is 4-116. Chloroform is with diffi- 
culty kindled, and burns with a greenish flame. It is nearly insoluble in 
water, and is not affected by concentrated sulphuric acid. Alcoholic solution 
of potassa decomposes it with production of chloride of potassium and for- 
mate of potassa. 

Chloroform may be prepared on a larger scale by cautiously distilling to- 
gether good commercial chloride of lime, water and alcohol. The whole 
product distils over with the first portions of water, so that the operation 
may be soon interrupted with advantage. 

This substance has been called strongly into notice from its remarkable 
effects upon the animal system in producing temporary insensibility to pain 
when its vapour is inhaled. 

Chloroform contains C 2 UC1 3 ; it is changed to formic acid by the substitu- 
tion of three eq. of oxygen for the three eq. of chlorine removed by the 
nlkaline metal. 



WOOD-SPIRIT AND ITS DERIVATIVES. 387 

Bromoform, C 2 HBr 3 , is a heavy, volatile liquid, prepared by a similar pro- 
cess, bromine being substituted in the place of chloiine. It is converted by 
alkali into bromide of potassium and formate of potassa. Iodoform, C 2 HI 3 , 
is a solid, yellow, crystallizable substance, easily obtained by adding alco- 
holic solution of potassa to tincture of iodine, avoiding excess, evaporating 
the whole to dryness, and treating the residue with water. Iodoform is 
nearly insoluble in water, but dissolves in alcohol, and is decomposed by al- 
kalis in the same manner as the preceding compounds. 

Formomethylal. — This is a product of the distillation of wood-spirit with 
dilute sulphuric acid and binoxide of manganese. The distilled liquid is 
saturated with potassa, by which the new substance is separated as a light 
oily fluid. When purified by rectification, it is colourless, and of agreeable 
aromatic odour; it has a density of 0-855, boils at 170° (41°C), and is com- 
pletely soluble in three parts of water. It contains C 6 H g 4 . It corresponds 
to acetal, and may be viewed as a compound of 2 eq. of ether, with 1 eq. 
of the yet unknown aldehyde of the methyl-series, C 6 H 8 4 =2C 2 H 3 0,C 2 H 2 2 . 

Methyl-mercaptan is prepared by a process similar to that recommended 
for ordinary mercaptan, sulphomethylate of potassa being substituted for 
the sulphovinate of lime. It is a colourless liquid, of powerful alliaceous 
odour, and lighter than water; it boils at 68° (20°C), and resembles mer- 
captan in its action on red oxide of mercury. 

Products of the action of chlorine on the compounds of methyl. — 
Chlorine acts upon the methylic compounds in a manner strictly in obedi- 
ence to the law of substitution ; the carbon invariably remains intact, and 
every proportion of hydrogen removed is replaced by an equivalent quantity 
of chlorine. Methylic ether and chlorine, in a dry and pure condition, 
yield a volatile liquid product, containing C 2 H 2 C10 ; the experiment is at- 
tended with great danger, as the least elevation of temperature gives rise to 
a violent explosion. This product in its turn furnishes, by the continued 
action of the gas, a second liquid, containing C 2 HC] 2 0. The whole of the 
hydrogen is eventually lost, and a third compound, C 2 C1 3 0, produced. 

Chloride of methyl, C 2 H 3 C1, in like manner gives rise to three successive 
products. The first, C 2 H 2 C1 2 , is a new volatile liquid, much resembling 
chloride of defiant gas ; the second, C 2 HC1 3 , is no other than chloroform ; 
the third is bichloride of carbon, C 2 C1 4 . 

Some of these substances, especially chloroform and bichloride of carbon, 
have been obtained also by the action of chlorine on light carbonetted hy- 
drogen (marsh-gas), which thus becomes connected with the methyl-series. 
It may be regarded as hydride of methyl, a view which is likewise sup- 
ported by its formation from zinc-methyl (see page 382) ; thus we have the 
following series. 

Hydride of methyl C 2 H 3 H. Light carbonetted hydrogen. 

Chloride of methyl C 2 H 3 C1. 

Chlorinetted chloride of methyl C 2 H 2 C1 2 . 
Bichlorinetted " " C 2 HC] 3 . Chloroform. 

Trichlorinetted " " C 2 C1 4 . Bichloride of carbon. 

The acetate of methyl, C 6 H 6 4 , gives CeH 4 Cl 2 4 , and C 6 rT 3 Cl 3 4 ; the other 
methyUethers are without doubt affected in a similar manner. 

Commercial wood-spirit is very frequently contaminated with other sub- 
stances, some of which are with great difficulty separated. It sometimes 
contains aldehyde, often acetone and propione, and very frequently a vola- 
tile oil, which is precipitated by the addition of water, rendering the whole 
turbid. The latter is a mixture of several hydrocarbons, very analogous to 
those contained in coal-tar. A specimen of wood-spirit, from Wattwyl, in 
Switzerland, was found by Gmelin to contain a volatile liquid, differing in 



388 POTATO-OIL AND ITS DERIVATIVES. 

some respects from acetone, to which he gave the term lignone. A very 
similar substance is described by Schweizer. and Weidmann, under the 
name of xylite. Lastly, Mr. Scanlan has obtained from wood-spirit a solid, 
yellowish-red, crystallizable substance called eblanin. It is left behind in 
the retort when the crude spirit is rectified from lime ; it is insoluble in 
water, sublimes without fusion at 273° (133° -9C), and contains, according 
to Dr. Gregory. C 2l H 9 4 . 

POTATO-OIL AND ITS DERIVATIVES. 

In the manufacture of potato-brandy the crude spirit is found to be con- 
taminated with an acrid volatile oil, called fusel-oil, which is extremely diffi- 
cult to separate in a complete manner. Towards the end of the distillation, 
it passes over in considerable quantity ; it may be collected apart, agitated 
with several successive portions of water to withdraw the spirit, with which 
it is mixed, and re- distilled. According to the researches of M. Cahours, 
this substance exhibits properties indicative of a constitution analogous to 
that of alcohol ; it may be considered as the hydrate of the oxide of the 
hydrocarbon, called amyl, containing C )0 H n . The ether of potato-oil, and 
a variety of other compounds, corresponding in every point to those of ordi- 
nary alcohol, have been formed, as will be manifest from an inspection of 
the following table : — 

Amyl (symbol Ayl) C 10 H n 

Amyl-ether C, H n O 

Hydride of amyl C 10 H n H 

Potato-oil C, H n O,HO 

Chloride of amyl C ]0 H n Cl 

Bromide of amyl C 10 H n Br 

Iodide of amyl C 10 H n I 

Zinc-amyl C 10 H n Zn 

Acetate of amyl C 10 H n O,C 4 H 3 O 3 

Sulphamylic acid C 10 H n O,2SO 3 ,HO 

Amylene C 10 H 10 

Valerianic acid , C 10 H 9 O 3 ,HO. 

Hydrated oxide or amyl; fusel oil; AylOJIO. — The crude fusel-oil 
of potato-brandy is washed with water, and distilled in a retort furnished 
with a thermometer, the bulb of which dips into the liquid. The portion 
which distils between 260° (126°-6C) and 280° (13.7°-8C) is collected apart 
and re-distilled in the same manner, until an oil is obtained, having a fixed 
boiling-point at 268° — 269° (131°-1C — 131°-7C). Thus purified, it is a 
thin fluid oil, exhaling a powerful and peculiarly suffocating odour, and 
leaving a burning taste ; it inflames with some difficulty, and then burns 
with a pure blue flame. Its density is 0818. It undergoes little change by 
contact with air under ordinary circumstances f but when warmed, and 
dropped upon platinum-black, it oxidizes to valerianic acid, which bears the 
same relation to this substance that acetic acid does to ordinary alcohol, or 
formic acid to methyl-alcohol. 

The action of heat upon fusel-oil has been lately studied by Captain 
Reynolds. The vapour of this alcohol, when passed through a red-hot glass- 
tube, yields a mixture of gases, among which a carbo-hyurogen CeH 6 pre- 
dominates, which has the chemical character of olefiant gas, and to which 
the name propylene has been given. The separation of this gaseous mixture 
lias hitherto failed, but on bringing the gas in contact with chlorine a 
compound C 9 H 6 C 2 is formed. This is a heavy liquid boiling at 21 7° -4 
(103°C). It is in every respect analogous to the Dutch-liquid (see page 
303), originating under similar circumstances from olefiant gas. 



POTATO-OIL AND ITS DERIVATIVES. 389 

Lmyl-ether, AylO. If amyl-alcohol is distilled -with concentrated sul- 

1 i-ric acid, a mixture of several substances is obtained, which has to be 
s.| irated by distillation. After several rectifications an oil is obtained, 
wh„eh has a sp. gr. 0-779 and boils at 348°-8 (176°C). This is aniyl-ether. 
The composition is C )0 H n O, or, if we adopt the double formula?, C 20 H 22 2 . 
Intermediate ethers between amyl- and ethyl-, and likewise between amyl- 
and methyl-ether have been prepared. They contain respectively C 14 Hi G 2 
= C 4 H 5 O,C 10 H u O and C 12 H 14 O 2 = C 2 H 8 O,C 10 H 11 O. 

Chloride of amyl, Ayl CI. — The chloride is procured by subjecting to 
distillation equal weights of potato-oil and pentachloride of phosphorus, 
washing the product repeatedly with alkaline water, and rectifying it from 
chloride of calcium. Less pure it may be obtained by saturating fusel-oil 
with hydrochloric acid. It is a colourless liquid, of agreeable aromatic 
odour, insoluble in water, and neutral to test-pape,r; it boils at 215° 
(101°-7C), and ignites readily, burniug'with a flame green at the edges. Ly 
the long-continued action of chlorine, aided by powerful sunshine, a new 
product, or chlorinetted chloride of amyl, was obtained in the form of a vola- 
tile colourless liquid, smelling like camphor, and containing C 10 H 3 C 9 ; the 
whole of the hydrogen could not, however, be removed. 

Bromide of amyl, Ayl Br, is a volatile, colourless liquid, heavier than 
water. It is obtained by distilling fusel-oil, bromine and phosphorus 
together. (See bromide of ethyl, page 353.) Its odour is penetrating and 
alliaceous. The bromide is decomposed by an alcoholic solution of potassa 
with production of bromide of the metal. 

Iodide of Amyl, Ayl I, is procured by distilling a mixture of 15 parts of 
potato-oil, 8 of iodine, and 1 of phosphorus. It is colourless when pure, 
heavier than water, volatile without decomposition at 294° -8 (146°C) and 
resembles in other respects the bromide ; it is partly decomposed by expo- 
sure to light. Iodide of amyl, when heated in sealed tubes with zinc to 
374° (190°C) yields amyl, a colourless liquid of an ethereal odour contain- 
ing C 10 H n , and boiling at 311° (155°C). Together with this substance 
there is formed iodide of zinc and zinc-amyl C 10 H n Zn, which, when coming 
in contact with water, is decomposed into oxide of zinc and hydride of amyl 
Ci H, 2 — C 10 H n H, which is an exceedingly volatile substance, boiling at 86° 
(3U°C). 

Cyanide of amyl, Ayl Cy. — Colourless liquid of 0-806 sp/gr., and boiling 
at 294° -8 (14G°C), which is obtained by distilling cyanide of potassium with 
sulphamylate of potassa. Boiled with potassa, this compound acid under- 
goes a decomposition analogous to that of cyanide of ethyl and methyl, (see 
pages 354 and 383;) it absorbs 4 eq. of water, and furnishes ammonia and 
the potassa-salt of caproic acid C l2 H 12 4 , one of the constituents of butter, 
C 12 H n N + 4HO=C 12 H 12 4 +NII 3 . 

Acetate of oxide of amyl, Ayl 0,C 4 H 3 3 . — This interesting product is 
easily obtained by submitting to distillation a mixture of 1 part of potato-oil, 

2 parts of acetate of potassa, and 1 part of concentrated sulphuric acid ; it is 
purified by washing with dilute alkali, and distillation from chloride of cal- 
cium. It presents the appearance of a colourless, limpid liquid, which is in- 
soluble in water, soluble in alcohol, boils at 272° (133°-3C), and becomes 
converted by an alcoholic solution of potassa into an acetate of that base, 
with reproduction of fusel-oil. This ether possesses in a remarkable manner 
the odour of the Jargonelle-pear. It is now manufactured upon a large 
scale for flavouring liquors and confectionary. 

Carbonate of oxide of amyl, Ayl 0,C0 2 . — This ether has been lately 
obtained by Mr. Medlock by saturating fusel-oil with phosgene-gas (chloro- 
carbonic acid). A compound analogous to chloro-carbonic ether AylO,C 2 C10,, 
is first produced, which, when treated with water, yields hydrochloric andcar- 



390 POTATO-OIL AND ITS DERIVATIVES. 

bonic acids, together with carbonate of amyl (AylO,C 2 C10 3 4-IIO==AylO, 

C0 2 +HCl-f-C0 2 ). Carbonate of amyl is a colourless liquid of an aromatic 

. boiling at 438°-8 (22G°C). Alcoholic solution of potassa converts 

her into fusel-oil, carbonate of potassa being formed at the same time. 

Sulphide of amyl, cmn/l-mercaptan, and numerous other compounds of like 
nature, have been described. 

iSuLPHAMYLic acid. — When equal weights of potato-oil and strong sul- 
phuric acid are mixed, heat is evolved, accompanied by blackening and par- 
tial decomposition. The mixture diluted with water, and saturated with 
carbonate of baryta, affords sulphate of that base, and a soluble salt cor- 
responding to the sulphovinate. The latter maybe obtained in a crystalline 
state by gentle evaporation, and purified by re-solution and the use of ani- 
mal charcoal. It forms small, brilliant, pearly plates, very soluble in water 
and alcohol, containing BaO,Cj H n O,2SO 3 -J-HO. The baryta may be pre- 
cipitated from the salt by dilute sulphuric acid, and the hydrated sulpha- 
mylic acid concentrated by spontaneous evaporation to a syrupy* or even 
crystalline state; it has an acid and bitter taste, strongly reddens litmus- 
paper, and is decomposed by ebullitio'h into potato-oil and sulphuric acid. 
The potassa-salt forms groups of small radiated needles, very soluble in 
water. The sulphamylates of lime and protoxide of lead are also soluble 
and crystallizable. 

Amylene. — By the distillation of potato-oil with anhydrous phosphoric 
acid, a volatile, colourless, oily liquid is procured, quite different in proper- 
ties from the original substance. It is lighter than water, boils at 102° -2 
(39°C), and contains no oxygen. Its composition is represented by the 
formula C 10 H 10 ; consequently it not only corresponds to the olefiant gas in 
the alcohol-series, but is isomeric with that substance. Like olefiant gas it 
combines directly with chlorine and bromine, giving rise to compounds 
Ci H 10 Cl 2 and Ci H I0 Br 2 . The vapour, however, has a density of 2G8, which 
is 2£ times that of olefiant gas, every measure containing 5 measures of 
hydrogen. 

Together with this substance several other hydrocarbons are formed, 
especially the one to which the name paramylene has been given. It con- 
tains C 20 H 20 , and boils at 320° (160°C). 

Valerianic or valeric acid. — M. Dumas has shown that when a mixture 
of equal parts of quicklime and hydrate of potassa is moistened with alcohol, 
and the whole subjected to a gentle heat, out of contact of air, the alcohol 
is oxidized to acetic acid, with evolution of pure hydrogen gas. At a higher 
temperature the acetate of potassa produced is in turn decomposed, yielding 
carbonate of potassa and light carbonetted hydrogen. Wood-spirit, by 
similar treatment, yields hydrogen and formate of potassa, which, as the 
heat increases, becomes converted into carbonate, with continued disengage- 
ment of hydrogen. In like manner potato-oil, the third alcohol, suffers under 
similar circumstances, conversion into a new acid, bearing to it the same 
relation that acetic acid does to common alcohol, and formic acid to wood- 
spirit, hydrogen being at the same time evolved. The body thus produced 
is found to be identical with a volatile oily acid distilled from the root Vale- 
riana officinalis. 

In preparing artificial valerianic acid, the potato-oil is heated in a flask 
with about ten times its weight of the above-mentioned alkaline mixture 
during the space of 10 or 12 hours ; the heat is applied by a bath of oil 
or fusible-metal raised to the temperature of 390° (198°-8C) or 400° 
(204°-4C). When cold, the nearly white solid residue is mixed with water, 
an excess of sulphuric or phosphoric acid added, and the whole subjected to 
distillation. The distilled liquid is supersaturated with potassa, evaporated 
nealy to dryness to dissipate any undecomposed potato-oil, and then mixed 



POTATO-OIL AND ITS DERIVATIVES. S91 

•with somewhat diluted sulphuric acid in excess. The greater part of the 
valerianic acid then separates as an oily liquid, lighter than water; this is a 
terhydrate of the acid, containing three equivalents of water, one of which 
is basic. When this hydrate is distilled alone, it undergoes decomposition ; 
water, with a little of the acid, first appears, and eventually the pure acid, 
in the form of a thin, fluid, colourless oil, of the persistent and characteristic 
odour of valerian-root. It has a sharp and acid taste, reddens litmus 
strongly, bleaches the tongue, and burns when inflamed with a bright, yet 
smoky light. Valerianic acid has a density of 0-937 ; it boils at 370° (175°C). 
Placed in contact with watei% it absorbs a certain quantity, and is itself to a 
certain extent soluble. The salts of this acid present but little interest, as 
few among them seem to be susceptible of crystallizing. The liquid acid is 
found by analysis to contain C 10 H 9 O 3 ,HO, and the silver-salt, AgO,C lc H s 3 . 
The ether-compound of valerianic acid has been already mentioned (page 
357). By treatment with ammonia this ether is converted into valeramide 
C 10 H n NO 2 =C 10 H 9 O 2 ,NH 2 , (analogous to acetamide,) which, under the influ- 
ence of anhydrous phosphoric acid loses 2 more eq. of water, becoming vale- 
ronitrile C 10 H 9 N=C 8 H 9 ,C 2 N or cyanide of butyl. The former is a fusible 
crystalline substance, the latter a volatile liquid, having a boiling point of 
257° (125°C). It was first obtained by the action of oxydizing agents upon 
gelatin. (See Section VIII on the components of the animal body.) 

A more advantageous mode of preparing valerianic acid is the following : 
— 4 parts of bichromate of potassa in powder, 6 parts of oil of vitriol, and 8 
parts of water are mixed in a capacious retort ; 1 part of pure potato-oil is 
then added by small portions, with strong agitation, the retort being plunged 
into cold water to moderate the violence of the reaction. "When the change 
appears complete, the deep green liquid is distilled nearly to dryness, the 
product mixed with excess of caustic potassa, and the aqueous solution sepa- 
rated mechanically from a pungent, colourless, oily liquid, which floats upon 
it, and which is valerianate of amyl. The alkaline solution is then evaporated 
to a small bulk and decomposed by sulphuric acid as already directed. 

Valerianic acid is found in angelica root, in the bark of Viburnum opulus, 
and probably exists in many other plants ; it is generated by the spontaneous 
decomposition of azotized substances, mineral and vegetable, and is produced 
in many chemical reactions in which oxidizing agents are employed. 

If au open jar be set in a plate containing a little water, and having beneath 
it a capsule with heated platinum-black, upon which potato-oil is slowly 
dropped in such quantity as to be absorbed by the powder, the sides of the 
jar become speedily moistened with an acid liquid, which collects in the 
plate, and maybe easily examined. This liquid, saturated with baryta-water, 
evaporated to dryness, and the product distilled with solution of phosphoric 
acid, yields valerianic acid. 1 

Some very beautiful, and for the progress of organic chemistry, highly 
important results, have lately been obtained by the action of electricity upon 
valerianic acid. By submitting a solution of valerianate of potassa to a gal- 
vanic current, produced by 4 elements of Bunsen's battery, Dr. Kolbe ob- 
served that potassa and pure hydrogen were evolved at the negative pole, 
while at the positive pole valerianic and carbonic acids, an odorous inflam- 
mable gas, and an ethereal liquid, made their appearance. The inflammable 
gas obtained in this reaction is a carbohydrogen C 8 H 8 which had been pre- 

1 Anhydrous valerianic acid is formed by the reaction between valerianate of potassa and 
oxychloride of phosphorus, 

5(KO. C10H9O3) and PC1 3 02=2KOP0 5; and 3KC1, and 5(CioII 9 07X 
It is an oleaginous liquid lighter than water. Boiling water changes it slowly into the 
hvdrated arid, while this transformation is rapidly affected by solutions of the alkalies. It 
boils at 410° (215°C). and distils unchanged— 11. B. 



392 POTATO-OIL AND ITS DERIVATIVES. 

viously isolated by Mr. Faraday from the oily products separated from rom- 
pressed oil gas. This substance, to which the name butylene has been given, 
is perfectly analogous to the olefiant gas (ethylene), propylene and amylene 
•which have been previously described. It combines with chlorine and bro- 
mine, forming substances analogous to Dutch liquid. The oily liquid formed 
together with amylene, in the electrolysis of valerianic acid, is a mixture of 
several substances, among which a hydrocarbon, of the remarkable compo- 
sition C 8 H 9 , predominates. This body, to which the name butyl or valyl has 
been given, is a colourless liquid, of an agreeable ethereal odour, and boils 
at 226°-4 (108°C). Kolbe believes that this hydrocarbon must be viewed 
as a compound analogous to methyl, ethyl, and amyl, with which we have 
become acquainted, and that it forms the radical of an alcohol yet to be dis- 
covered, having the formula C 8 H O, HO and analogous to methyl-, ethyl-, and 
amyl-alcohols, an alcohol which, by oxidation, would yield the acid C 8 H 7 3 , 
HO, i. e., but3 r ric acid, just as the three alcohols mentioned are converted 
respectively into formic, acetic, and valeric acids. Kolbe considers butyl to 
be one of the proximate constituents of valeric acid, which he views as an 
intimate combination of butyl with oxalic acid, butyl-oxalic acid C 10 H 9 O 3 ,HO 
=C 8 H 9 ,C 2 3 HO. According to this view, the transformation of valeric acid 
under the influence of the galvanic current is readily explained. The oxy- 
gen evolved at the positive pole by the electrolysis of water oxidizes the oxa- 
lic to carbonic acid, and liberates the butyl, portions of which are farther 
attacked by the oxygen, and deprived of 1 eq. of hydrogen, thus giving rise 
to the simultaneous evolution of butylene. If this view holds good for butyric 
acid, it must be equally true of propionic, acetic, and formic acid, and of a 
great number of analogous acids, which will be described in the subsequent 
chapters of this Manual. 

Propionic acid will be ethyl-oxalic acid, acetic acid methyl-oxalic, and 
lastly, formic acid hydrogen- oxalic acid, thus — 

Formic acid C 2 H0 3 , H0= H ,C 2 3 ,HO 

Acetic acid , C 4 H 3 3 ,HO=C 2 H 3 ,C 2 3 ,HO 

Propionic acid C 6 I] 5 3 ,HO=C 4 H.,C 2 3 ,HO 

Valeric acid C 10 H 9 O 3 ,HO=C 8 H 9 ,C 2 O 3 ,HO 1 

This view is borne out by the electrolytic decomposition of acetic acid, which 
yields a gas, considered by Kolbe to be methyl. Several collateral facts have 
furnished additional support to this theory, amongst which may be quoted 
the remarkable deportment of the ammonia-salts of these acids under the 
influence of anhydrous phosphoric acid. In this reaction, oxalic, formic, 

* Butyric acid constitutes the fifth member of this series as a combination of propyl with 
oxalic acid or propyl-oxalic acid, 

Butyric acid CsHgO^IIO^CeHyAO^HO 

As valyl is formed from valeric acid, so the decomposition of butyric acid should yield propyl 
CcTI 7 , the oxide of which C0II7O has bien detected in cod-liver oil in combination with oleic 
and margaric acid. 

Butylic alcohol of Wurtz appears to fill up this vacancy in the alcohol serier.. It was 
extracted from rectified potato-oil by fractional distillations, retaining that which passes 
between 22(i°-4 (103°) and 2-H°-4 (118°). By subsequent purification a liquid is obtained which 
boils at 233° - 6(112°), is lighter than water, lias the odour of amylic alcohol, but less disagree- 
able. Fused potassa changes it into butyric acid with the liberation of hydrogen. Its com- 
position is CpII]o02=C 8 ri 9 0,HO, or hydrate of oxide of valyl. 

Butylic alcohol, when mixed with its own weight of strong sulphuric acid and after twenty- 
four hours' repose saturated with carbonate of potassa, yields sulphate and sulphobutylate 
of potassa. The latter dissolves readily in boiling absolute alcohol, froni which it is deposited 
in anhydrous pearly crystals of the composition KO,CsIIs>0.2S03. 

The cyanate and cyanurate of bulylic ether yield with potassa a nitrogenous product, 
butylamin, NIto0 8 Itr>,"in the same way as the cyanates and cyanurates of ethyl, methyl, or 
amyl, yield respectively ethylamin, NHaCiHs, mcthylamin NllaCjIls, and amylamin Nlba 
CioHii.— K. B. 



FUSEL-OIL OF GRAIN-SPIRIT. 393 

acetic, propionic, and valeric acids yield respectively cyanogen and the cya- 
nides of hydrogen, methyl, ethyl, and butyl. 

NH 4 0, C 2 3 — 4HG= C„N 

KII 4 0, H, C a Q 3 — 4HO= R, C^N 

NH 4 0,C 2 H 3 ,C 2 3 — 4HO = C 2 H 3 ,C 2 >J 

NH 4 0,C 4 H 5 ,C 2 3 — 4HO=C 4 H 5 ,C 2 N" 

NH 4 0,C 8 H 9 ,C 2 3 — 4HO=C 8 H 9 ,C 2 N 

We have seen, moreover, that the cyanides of methyl and ethyl, when treated 
"with the alkalis are readily reconverted into acetic and propionic acid, and 
in the Section on cyanogen it -will be shown that this substance and hydro- 
cyanic acid are indeed easily convertible into oxalate and formate of ammonia. 
All these facts are readily intelligible by the view proposed by Dr. Kolbe. 

Chlorovalerisic acid. — When dry chlorine is passed for a long time into 
pure valerianic acid, in the dark, the gas is absorbed in great quantity, and 
much hydrochloric acid produced ; towards the end of the operation a little 
heat becomes necessary. The product is a semi-fluid transparent substance, 
heavier than water, odourless, and of acrid burning taste. It does not congeal 
■when exposed to a very low temperature, but acquires complete fluidity when 
heated to 86° (30°C). It cannot be distilled without decomposition. When 
put into water it forms a thin, fluid hydrate, which afterwards dissolves to a 
considerable extent. This body is freely soluble in alkalis, from which it is 
again precipitated by the addition of an acid. Chlorovalerisic acid contains 
C 10 (H 6 C1 3 )0 3 ,HO. 

Chlorovalerosic acid. — This is the ultimate product of the action of 
chlorine on the preceding substance, aided by exposure to the sun. It re- 
sembles chlorovalerisic acid in appearance and properties, being semi-fluid 
and colourless, destitute of odour, of powerful pungent taste, and heavier 
than water. It can neither be solidified by cold, nor distilled without decom- 
position. In contact with water, it forms a hydrate containing 3 eq. of that 
substance, which is slightly soluble. In alcohol and ether it dissolves with 
facility. It forms salts with bases, of which the best defined is that of silver. 
Chlorovalerosic acid is composed of C ]0 (H 5 Cl 4 )O 3 ,HO. 

Fusel-oil of grain-spirit. — The fusel-oil separated in large quantities 
from grain-spirit by the London rectifiers consists chiefly of potato-oil (hy- 
drated oxide of amyl) mixed with alcohol and water. Sometimes it contains 
in addition more or less of the ethyl- or amyl-compounds of certain fatty 
acids thought to have been identified with cenanthic and margaric acids. 
These last-named substances form the principal part of the nearly solid fat 
produced in this manner in whisky-distilleries conducted on the old plan. 
Mulder has described, under the name of corn-oil, another constituent of the 
crude fusel-oil of Holland ; it has a very powerful odour resembling that of 
some of the umbelliferous plants, and is unaffected by solution of caustic 
potassa. According to Mr. Rowney, the fusel-oil of the Scotch distilleries 
contains in addition a certain quantity of capric acid C 20 H 20 O 4 which is one 
of the constituents of butter. 

The fusel-oil of marc-brandy of the south of France was found by M. Balard 
to contain potato-oil and cenanthic ether. Potato-oil has been separated from 
the spirit distilled from beet-molasses, and from artificial grape-sugar made 
by the aid of sulphuric acid. Although much obscurity yet hangs over the 
history of these substances, it is generally supposed that they are products 
of the fermentation of sugar, and have an origin contemDoraneous with thai 
of common alcohol. 



It is impossible to leave the history of the alcohols without alluding to 
some results of great importance for the elucidation of organic compounds 



394 HOMOLOGOUS SERIES. 

generally, which the study of these substances has elicited. When describing 
the three alcohols, discussed in the preceding chapter, we have repeatedly 
pointed out the remarkable analogy presented by the properties and the 
general deportment of these three bodies. If we compare the composition 
of the three alcohols, 

Methyl-alcohol C 2 H 4 2 

Ethyl-alcohol C 4 H 6 2 

Amyl-alcohol C 10 H l2 O 2 

we find that their formulae present an unmistakable symmetry. All three 
contain the same amount of oxygen, only the carbon and hydrogen vary. 
This variation, however, takes place in very simple relations. Thus we find 
the difference of ethyl- and methyl-alcohol to be C 4 H 6 2 — C 2 H 4 2 = C 2 H 2 , 
the difference of amyl- and methyl-alcohol to be C 10 H 12 O 2 — C 2 H 4 2 = C 8 H 8 
=4C 2 H 2 . The same elementary difference of course prevails likewise be- 
tween all the derivatives of the three alcohols. 

Iodide of methyl C 2 H 3 I 

Iodide of ethyl C 4 H 5 I = C 2 F 3 I -f C 2 H 2 

Iodide of amy! C 10 H n I = C 2 H 3 I -}- 4C 2 H 2 

or 

Formic acid C 2 H 3 ,HO 

Acetic acid C 4 K 3 3 ,HO = C 2 H0 3 ,HO-f C 2 F 2 

Valeric acid C 10 H 9 3 ,HO = C 2 H0 3 ,HO-j-4C 2 H 2 

Methylic, ethylic, and amylic alcohols are by no means the only members 
of this class which are known. In the succeeding sections of this work will 
be noticed a series of compounds evidently of a perfectly analogous character 
which have been discovered. By submitting castor-oil to a series of pro- 
cesses, M. Bouis has formed an alcohol, which has been called "caprylio 
alcohol." According to M. Dumas, spermaceti contains another analogous 
substance, cetylic alcohol, which is a solid : and Mr. Brodie has prepared 
two alcohols, cerotylic and mellisic, from ordinary bees' wax. The compo- 
sition of these substances stands in exactly the same relation to that of the 
preceding alcohols, which we have pointed out, as will be seen from the fol- 
lowing table : — 

Caprylic alcohol C, 6 H 18 2 = C 2 H 4 2 -f 7C 2 H 2 

Cetylic alcohol C 32 H 34 2 = C 2 H 4 2 -f 15C 2 EI 2 

Cerotylic alcohol C^H 56 2 = C 2 H 4 2 -f 26C 2 H 2 

Melissic alcohol C 60 H 62 O 2 = C 2 H 4 2 -f 29C 2 H 2 

These four alcohols, when submitted to the action of oxidizing agents, are 
converted into four acids, analogous to formic and acetic acid, and which 
stand to each other, and to formic and acetic acid, in exactly the same rela- 
tion as the various alcohols. 

Caprylic acid C 16 K 15 3 ,HO = C 2 H0 3 ,HO -f 7C 2 B 2 

Cetylic acid C 32 H 31 3 ,HO = C 2 H0 3 ,HO -f- 15C 2 H 2 

Cerotylic acid C 54 H 53 3 ,HO = C 2 H0 3 ,HO -f 26C 2 H 2 

Melissic acid C 60 H 69 O 3 ,HO = C 2 H0 3 ,HO -f 29C 2 H 2 

A glance at these tables shows that all the alcohols known differ from 
methyl-alcohols by C 2 H 2 , or a multiple of it. At the same time, it is evi- 
dent that the series by no means regularly ascends. Thus we perceive that 
between ethylic and amylic alcohols two compounds are possible ; in like 
manner two between amylic and caprylic alcohols. 

Even now the parallel series of volatile acids is far more complete than 



HOMOLOGOUS SERIES. 395 

that of the alcohols. At present the following members of this group are 
known, which are placed in juxtaposition with the collateral alcohols: — 

Methyl-alcohol C 2 H 4 2 Formic acid C 2 H 2 4 

Ethyl-alcohol C 4 H 6 2 Acetic acid C 4 H 4 4 

(Tetryl-alcohol) C 6 H s 2 Propionic acid C 6 H 6 4 

(Butyl-alcohol) C 8 H 10 O 2 Butyric acid C 8 H g 4 

Amyl-alcohol C 10 H j2 O 2 Valeric acid C 10 H 10 O 4 

C 12 H 14 2 Caproic acid C ]2 H 12 4 

C 14 H 16 2 (Enanthylic acid C l4 H 14 4 

Capryl-alcohol c i 6 H i8°2 Caprylic acid C i 6 H it>°4 

C i8 H 20 O 2 Pelargonic acid C ]s H 18 4 

C 20 H 22°2 Capric acid C 20 H 20 Q 4 

&c. &c. &c. &c. 

We might continue the series of acids uninterruptedly 'to C 38 H 3S 4 (balenic 
acid), and with intervals even much higher up to acids containing 54 and 
even more equivalents of carbon. Most of the acids belonging to this series 
have been separated from fats, and hence this series is frequently designated 
by the name of the series of fatty acids. 

A series of analogous substances whose composition varies by C 2 H 2 , or a 
multiple of it, is called a series of homologous bodies — a name first used by 
M. Gerhardt, to whom we are much indebted for the elucidation of this sub- 
ject. It is evident that there exist as many such homologous series as there 
are derivatives of any one of the alcohols. We may construct a series of 
homologous radicals, or ethers, or hydrocarbons. 

Methyl C 2 H 3 Methyl- ether.. C 2 E 3 C 2 F 2 

Ethyl C 4 H 5 Ether C 4 H 5 Ethylene C 4 H 4 

Propyl ? .... C 6 H 7 (Tetryl-ethcr). C P H 7 Propylene .... C 6 H 6 

Butyl C s H 9 C- II 9 Butylene C s H 8 

Amyl C 10 H n Amyi-ether.... C, H n O Amylene Ci H I0 

Caproyi .... C l2 H u C,,H 13 Caproylene... C ]2 H ]2 

C 14 H 15 C; 4 H 15 C 14 H 14 

C 16 H 17 C 16 H 17 Caprylene .... C l6 H ]6 

All these series of homologous bodies still present numerous gaps ; none 
perhaps more than that of the alcohols which may be taken as the prototype 
of all the rest ; but since the existence of these homologous series was first 
pointed out, many gaps have been filled, and it may be expected that before 
long the rapid strides of organic chemistry will render them complete. 

The properties of the various members belonging to homologous series 
gradually change as we ascend in the series. The most characteristic alte- 
ration is the diminution of volatility. A regular difference between the 
boiling points of homologous substances was first pointed out by H. Kopp 
As an example may be taken the series of fatty acids : — 

Boiling points. Differences. 

F. C. F. C. 



Formic acid C 2 F 2 4 209° 98 ( 

Acetic acid C 4 H 4 4 246° 11! 

Propionic acid C 6 II 6 4 284° 140° 



20°- 
21° 



30° 



Butyric acid C 8 H 8 4 314°-6 157° ) ^ , 

Valeric acid C ln H ln 4 347° 175° M °* n * i° 



•4 198° 



1 410.4 23° 



From this table it is evident that the boiling temperature of the homolo- 
gous acids rises on an average 36° -3 (19°-9Cj for every increment of CH^ 
A similar regular difference has been observed in the boiling points of manj 



396 BITTER- ALMOND OIL 

homologous compounds. As yet, however, the number of cases in "which 
discrepancies occur is very considerable. 

The substances discussed in the next three sections have but little relation 
to the alcohols ; they may, however, be here most conveniently described. 

BITTER-ALMOND OIL AND ITS PRODUCTS. 

The volatile oil of bitter almonds possesses a very high degree of interest, 
from its study having, in the hands of MM. Liebig and Wohler, led to the 
first discovery of a compound organic body capable of entering into direct 
combination with elementary principles, as hydrogen, chlorine, and oxygen, 
and playing in some degree the part of a metal. The oil is supposed to be 
the hybride of a salt-basyle, containing C ]4 H 5 2 , called benzoyl, from its re- 
lation to benzoic acid, which radical is to be traced throughout the whole 
series ; it has been isolated, and will be described among the products of 
distillation of the benzoates. 

Table of Benzoyl- Compounds. 

Benzoyl, symbol Bz C 14 H 5 2 

Hydride of benzoyl; bitter-almond oil C 14 H 5 2 rI 

Hydrated oxide of benzoyl; benzoic acid C 14 H 5 2 0,HO 

Chloride of benzoyl C 14 H 5 2 C1 

Bromide of benzoyl C 14 H 5 2 Br 

Iodide of benzoyl C 14 H 5 2 T 

Sulphide of benzoyl C 14 H 5 2 S. 

Hydride of benzoyl ; bitter-almond oil ; BzH. — This substance is pre- 
pared in large quantities, principally for the use of the perfumer, by dis- 
tilling with water the paste of bitter almonds, from which the fixed oil has 
been expressed. It certainly does not pre-exist in the almonds; the fat oil 
obtained from them by pressure is absolutely free from every trace of this 
principle ; it is formed by the action of water upon a peculiar crystallizable 
substance, hereafter to be described, called amygdalin, aided in a very ex- 
traordinary manner by the presence of the pulpy albuminous matter of the 
seed. The crude oil has a yellow colour, and contains a very considerable 
quantity of hydrocyanic acid, the origin of which is contemporaneous with 
that of the oil itself: it is agitated with dilute solution of protochloride of 
iron mixed with hydrate of lime in excess, and the whole subjected to dis- 
tillation; water passes over, accompanied by the purified essential oil, which 
is to be left for a short time in contact with a few fragments of fused chlo- 
ride of calcium to free it from water. 

Pure hydride of benzoyl is a thin, colourless liquid, of great refractive 
power, and peculiar and very agreeable odour; its density is 1-043, and its 
boiling-point 856° (180°C): it is soluble in about 80 parts of water, and is 
miscible in all proportions with alcohol and ether. Exposed to the air, it 
greedily absorbs oxygen, and becomes converted into a mass of crystallized 
benzoic acid. Heated with hydrate of potassa, it disengages hydrogen, and 
yields benzoate of the base. The vapour of the oil is inflammable, and burns 
with a bright flame and much smoke. It is very doubtful whether pure 
bitter-almond oil is poisonous ; the crude product, sometimes used for im- 
parting an agreeable flavour to puddings, custards, &c, and even publicly 
sold for that purpose, is in the highest degree dangerous. 

Oxide of benzoyl ; benzoic acid ; BzO. — This is the sole product of the 
oxidation at a moderate temperature of bitter-almond oil ; it is not, how- 
ever, thus obtained for the purposes of experiment and of pharmacy. Seve- 
ral of the balsams yield benzoic acid in great abundance, more especially 
the concrete resinous variety known under the name of gum-benzoin. When 




AND ITS PRODUCTS. 397 

this substance is exposed to a gentle heat in a subliming vessel, the benzoic 
acid is volatilized, and may be condensed by a suitable arrangement. The 
simplest and most efficient apparatus for this and all 
similar operations is the contrivance of Dr. Mohr : Fig. 171. 

it consists of a shallow iron pan, (fig. 171,) over the 
bottom of which the substance to be sublimed is thinly 
spread ; a sheet of bibulous-paper, pierced with a 
number of pin-holes, is then stretched over the vessel, 
and a cap made of thick, strong drawing or cartridge- 
paper, secured by a string or hoop over the whole. 
The pan is placed upon a sand-bath and slowly heated 
to the requisite temperature ; the vapour of the acid 
condenses in the cap, and the crystals are kept by the 
thin paper diaphragm from falling back again into the 
pan. Benzoic acid thus obtained assumes the form of 
light, feathery, colourless crystals, which exhale a fragrant odour, not 
belonging to the acid itself, but due to the small quantity of a volatile oiL 
A more productive method of preparing the acid is to mix the powdered gum- 
benzoin very intimately with an equal weight of hydrate of lime, to boil 
this mixture with water, and to decompose the filtered solution, concentrated 
by evaporation to a small bulk, with excess of hydrochloric acid ; the benzoic 
acid crystallizes out on cooling in thin plates, which may be drained upon a 
cloth, filter, pressed, and dried in the air. By sublimation, which is then 
effected with trifling loss, the acid is obtained perfectly white. 

Benzoic acid is inodorous when' cold, but acquires a faint smell when gently 
warmed; it melts just below 212° (100°C), and sublimes at a temperature a 
little above; it boils at 462° (238°-8C), and emits a vapour of the density 
of 4-27. It dissolves in about 200 parts of cold, and 25 parts of boiling 
water, and with great facility in alcohol. Benzoic acid is not affected by 
ordinary nitric acid, even at a boiling heat. The crystals obtained by sub- 
limation, or by the cooling of a hot aqueous solution, contain an equivalent 
of water, which is basic, or C, 4 H 5 3 ,HO. 

All the benzoates have a greater or less degree of solubility ; they are 
easily formed, either directly or by double decomposition. Benzoates of the 
alkalis and of ammonia are very soluble, and somewhat difficult to crystallize. 
Benzoate of lime forms groups of small colourless needles, which require 20 
parts of cold water for solution. The salts of baryta and strontia are soluble 
with difficulty in the cold. Neutral benzoate of the sesquioxide of iron is a 
soluble compound ; but the basic salt obtained by neutralizing as nearly as 
possible by ammonia a solution of sesquioxide of iron, and then adding ben- 
zoate of ammonia, is quite insoluble. Sesquioxide of iron is sometimes thus 
separated from other metals in practical analysis. Neutral and basic 
benzoate of lead are freely soluble in the cold. Benzoate of silver crystallizes 
in thin transparent plates, which blacken on exposure to light. Some re- 
markable products, obtained by the action of chlorine upon a solution of 
benzoate of potassa, will be mentioned in the section on the Organic Bases. 

Nitkobenzoic acid. — rr-When benzoic acid is boiled for several hours with 
fuming nitric acid, until red fumes cease to appear, it yields a new acid body, 
in which the elements of hyponitric acid are substituted for an equivalent of 
hydrogen of the original benzoic acid. Nitro-benzoic acid greatly resembles 
benzoic acid in character, and contains C 14 H 4 N0 7 ,HO=C 14 (H 4 N0 4 )0 3 ,HO. 
The remarkable transformation of the amide of this acid, of nilro-benzrimide, 
will be noticed under the head of aniline. 

Sulphobexzoic acid. — Benzoic acid is soluble without change in concen 
trated oil of vitriol, and is precipitated by the addition of water ; it combines, 
however, with anhydrous sulphuric acid, generating a compound acid analo* 
34 



398 BITTER-ALMOND OIL 

gous to the sulphovinic, but bibasic, forming a neutral and an acid series of 
salts. The baryta-compound is easily prepared by dissolving in water the 
viscid mass produced by the union of the two bodies, and saturating the 
solution with carbonate of baryta. On adding hydrochloric acid to the filtered 
liquid, and allowing the whole to cool, acid sulphobenzoate of baryta crys- 
tallizes out. This salt has an acid reaction, and requires 20 parts of cold 
water for solution ; the neutral salt is much more soluble. The hydrated 
acid is easily-obtained by decomposing the sulphobenzoate of baryta by dilut . 
sulphuric acid ; it forms a white, crystalline, deliquescent mass, very stabh, 
and permanent, which contains C ]4 H 5 3 ,2S0 3 ,2HO. 

Benzone, benzophenone. — When dry benzoate of lime is distilled at a high 
temperature, it yields a thick, oily, colourless liquid, of peculiar odour. This 
is a mixture of several compounds, from which, however, a crystalline sub- 
stance C 13 H 5 0, or C 26 H 10 O 2 , may be isolated, to which the name benzone or 
benzophenone has been given. Carbonate of lime remains in the retort; the 
reaction is thus perfectly analogous to that by which acetone is produced by 
the distillation of a dry acetate. 

CaO,C 14 H 5 3 =C 13 H 5 0-f CaO,C0 2 . 

The benzophenone is, however, always accompanied by secondary products, 
due to the irregular and excessive temperature, solid hydrocarbons, carbonic 
oxide, and benzol, a body next to be described. 

Benzol, or Benzine. — If crystallized benzoic acid be mixed with three 
times its Weight of hydrate of lime, and the whole distilled at a temperature 
slowly raised to redness in a coated glass or earthen retort, water, and a 
volatile oily liquid termed benzol, pass over, while carbonate of lime, mixed 
with excess of hydrate of lime, remains in the retort. The benzol separated 
from the water, and rectified, forms a thin, limpid, colourless liquid, of strong 
agreeable odour, insoluble in water, but miscible with alcohol, having a den- 
sity of 0-885, and boiling at 176° (80°C) ; the sp. gr. of its vapour is 2-738. 
Cooled to 32° (0°C), it solidifies to a white, crystalline mass. Benzol contains 
carbon and hydrogen only, in the proportion of 2 eq. of the former to 1 of 
the latter, or probably C 12 H 6 . It is produced by the resolution of the benzoic 
acid 'into benzol and carbonic acid, the water taking part in the reaction. 

C 14 H 6 4 =C 12 H 6 -f2C0 2 . 

Benzol is identical with the bicarbide of hydrogen, many, years ago dis- 
covered by Mr. Faraday in the curious liquid condensed during the compres- 
sion of oil-gas, of which it forms the great bulk, being associated with an 
excessively volatile hydrocarbon, containing carbon and hydrogen in the 
ratio of the equivalents, the vapour of which required for condensation a 
temperature of 0° ( — 17°-7C). This is the substance which has been de- 
scribed under the name of butylene, when treating of valeric acid (see page 
- 392). 

A copious source of benzol has been lately shown by Mr. Mansfield to exist 
in the lightest and most volatile portions of coal-tar oil, which will be noticed 
in its place under the head of that substance. 

Sclphobenzide and HYPOsuLrHOBENZic acid. — Benzol combines directly 
with anhydrous sulphuric acid, to a thick viscid liquid, soluble in a small 
quantity of water, but decomposed by a larger portion, with separation of a 
crystalline matter, the sulphobenzide, which may be washed with water, in 
which it is nearly insoluble, dissolved in ether, and left to crystallize by 
spontaneous evaporation. It is a colourless, transparent substance, of great 
importance, fusible at 212° (100°C), bearing distillation without change, and 
resisting the action of acids and other energetic chemical agents. Sulpho- 
benzide contains C l2 H 5 S0 2 . It may be viewed as benzol in which 1 eq. of 



AND ITS PRODUCTS. 399 

hydrogen has been replaced by 1 eq. of sulphurous acid. The acid liquid 
from which the preceding substance has been separated, neutralized by 
carbonate of baryta and filtered, yields hyposulphobenzate of baryta, which is 
a soluble salt, but crystallizes in an imperfect manner. By double decompo- 
sition with sulphate of copper, a compound of the oxide of that metal is 
obtained, which forms fine, large, regular crystals. The hydrate of hyposul- 
phobenzic acid is prepared by decomposing the copper-salt with sulphuretted 
hydrogen ; a sour liquid is obtained, which furnishes, by evaporation, a 
crystalline residue, containing C ]2 H 5 S0 2 -j-HO,S0 3 . The salts of potassa, 
soda, ammonia, and of the oxides of zinc, iron, and silver, crystallize freely. 
This compound acid can be prepared by dissolving benzol in Nordhausen 
sulphuric acid. 

Nitrobenzol. — Ordinary nitric acid, even at a boiling temperature, has no 
action on benzol ; the red fuming acid attacks it, with the aid of heat, with 
great violence. The product, on dilution, throws down a heavy, oily, yel- 
lowish, and intensely sweet liquid, which has an odour resembling that of 
bitter-almond oil. Its density is 1-209; it boils at 415° (212°-8C), and dis- 
tils but not without being slightly changed. It is but little affected by acids, 
alkalis, or chlorine, and is quite insoluble in water. Nitrobenzol contains 
C 12 H 5 N0 4 , and may be viewed as benzol, in which 1 eq. of hydrogen is re- 
placed by 1 eq. of hyponitric acid. "When nitrobenzol is heated with an al- 
coholic solution of caustic potassa, and the product subjected to distillation, 
a red oily liquid passes over ; this is a mixture of several substances from 
which, on cooling, large red crystals separate, which are nearly insoluble in 
water, but dissolve with facility in ether and alcohol. This compound, 
which is called azobenzol, melts at 149° (65°), and boils at 379° (192° -2C) ; 
it contains C 12 H 5 N. Together with the azobenzol an oil is produced, which 
contains C ]2 H 7 N, and has, like ammonia, the power of combining with acids. 
It has received the name of aniline, and will be described in the section on 
organic bases. The reaction which gives rise to azobenzol and aniline in 
this case, is not yet perfectly understood, several other substances being si- 
multaneously produced, and a large quantity of nitrobenzol being charred. 
Nitrobenzol may, however, be entirely converted into aniline, by a most ele- 
gant process, discovered by Zinin, namely, by the action of sulphide of am- 
monium, which will be noticed when treating of aniline. 

Binitrobenzol. — If benzol is dissolved in a mixture of equal volumes of 
concentrated nitric and sulphuric acids, and the liquid be boiled for some 
minutes, it solidifies on cooling to a mass of crystals, which are easily fu- 
sible, insoluble in water, and readily soluble in alcohol. They contain C 12 H 
N 2 8 =C ]2 (H 4 2N0 4 ), and may be viewed as benzol in which 2 eq. of hydrogen 
are replaced by 2 eq. of hyponitric acid. 

Benzol and chlorine combine when exposed to the rays of the sun ; th<! 
product is a solid, crystalline, fusible substance, insoluble in water, contain- 
ing C 12 H 6 Cl,j, called chlorobenzol When this substance is distilled, it is de- 
composed into hydrochloric acid, and a volatile liquid, chlorobenzide, composed 
of C 12 H 3 C1 3 . 

In its chemical relations, benzol exhibits the character of a substance anal- 
ogous to hydride of methyl (marsh-gas), hydride of ethyl, and hydride of 
ainyl. 

Benzol C 12 H 5 H. = Hydride of Phenyl. 

Sulphobenzol C 12 H 5 S0 2 . 

Nitrobenzol C, 2 H 5 N0 4 . 

The alcohol belonging to this hydride is known; it contains C ]2 rl 6 2 — 

C 12 H 5 0,HO, and will be described among the volatile principles of coal-tar 

Chloride of benzoyl, BzCl. — This compound is prepared by passing drif 



400 BITTER-ALMOND OIL 

chlorine gas through pure bitter-almond oil, as long as hydrochloric acid 
continues to be formed ; the excess of chlorine is then expelled by heat. 
Chloride of benzoyl is a colourless liquid of peculiar, disagreeable, and pun- 
gent odour. Its density is 1-106. The vapour is inflammable, and burns 
with a tint of green. It is decomposed slowly by cold, and quickly by boil- 
ing water, into benzoic and hydrochloric acids ; with an alkaline hydrate, 
benzoate of the base, and chloride of the metal, are generated. 

Benzamide. — When pure chloride of benzoyl and dry ammoniacal gas are 
presented to each other, the ammonia is energetically absorbed, and a white, 
solid substance produced, which is a mixture of sal-ammoniac and a highly 
interesting bod}% benzamide. The sal-ammoniac is removed by washing with 
cold water, and the benzamide dissolved in boiling water, and left to crys- 
tallize. It forms colourless, transparent, prismatic, or platy crystals, fusible 
at 239° (115°C), and volatile at a higher temperature. It is but slightly 
soluble in cold, freely in boiling water, also in alcohol and ether. Benza- 
mide corresponds to oxamide, both in composition and properties ; it con- 
tains C 14 H 7 N02=C ]4 H 5 2 ,NH 2 , or benzoate of oxide of ammonium, minus 2 
eq. of water, and it sutlers decomposition by both acids and alkaline solu- 
tions, yielding, in the first case, a salt of ammonia and benzoic acid, and, in 
the second, free ammonia and a benzoate. When distilled it loses again 2 
eq. of water, and becomes benzonitrile. (See farther on.) 

Iodide of Benzoyl, Bzl. — This is prepared by distilling the chloride of 
benzoyl with iodide of potassium ; it forms a colourless, crystalline, fusible 
mass, decomposed by water and alkalis, in the same manner as the chloride. 
The bromide of benzoyl, BzBr, has very similar properties. The sulphide, 
BzS, is a yellow oil, of offensive smell, which solidifies, at a low temperature, 
to a soft, crystalline mass. Cyanide of benzoyl, BzCy, obtained by heating 
the chloride with cyanide of mercury, forms a colourless, oily, inflammable 
liquid, of pungent odour, somewhat resembling that of cinnamon. All 
these compounds yield benzamide with dry ammonia. 

Formobenzoic acid. — Crude bitter-almond oil is dissolved in water, mixed 
with hydrochloric acid, and evaporated to dryness.: the residue is boiled 
with ether, which dissolves out the new substance, and leaves sal-ammoniac. 
Formobenzoic acid forms small, indistinct, white crystals, which fuse, and 
afterwards suffer decomposition by heat, evolving an odour resembling that 
of the flowers of the hawthorn, and leaving a bulky residue of charcoal. It 
is freely soluble in water, alcohol, and ether, has a strong acid taste and reac- 
tion, and forms a series of crystallizable salts with metallic oxides. This sub- 
stance contains C ]6 H 7 5 ,HO==C 14 H 6 2 --|-C 2 H03,HO, or the elements of bitter- 
almond oil, and formic acid : it owes its origin to the peculiar action of strong 
mineral acids on the hydrocyanic acid of the crude oil, by Avhich that body 
suffers resolution into formic acid and ammonia. It is decomposed by oxi- 
dizing bodies, as binoxide of manganese, nitric acid, and chlorine, into bitter- 
almond oil and carbonic acid. 

Hydrobenzamide. — Pure bitter-almond oil is digested for some hours at 
about 120° (49°C) with a large quantity of strong solution of ammonia ; the 
resulting white crystalline product is washed with cold ether, and dissolved 
in alcohol; the solution, left to evaporate spontaneously, deposits the hydro- 
benzamide in regular, colourless crystals, which have neither taste nor smell. 
This substance melts at a little above 212° (100°C), is readily decomposed 
by heat, dissolves with ease in alcohol, but is insoluble in water ; the alco- 
holic solution is resolved by boiling into ammonia and bitter-almond oil ; a 
similar change happens with hydrochloric acid. Hydrobenzamide contains 
<' 4? 1I |C N 2 , or the elements of 3 equivalents of bitter-almond oil, and 2 of 
ammonia, minus 6 equivalents of water. When impure bitter-almond oil is 
employed in this experiment, the products are different, several other com- 



AND ITS PRODUCTS. 401 

pounds being obtained. But even with the pure oil frequently a great variety 
of substances are formed. The hydrobenzanride when submitted to the action 
of chemical processes furnishes a great number of derivatives, of which, how- 
ever, only one substance, namely, amarine, will be described in the section 
on the organic bases. 

Benzoin. — This substance is found in the residue contained in the retort 
from which bitter-almond oil has been distilled with lime and oxide of iron, 
to free it from hydrocyanic acid ; it is a product of the action of alkalis and 
alkaline earths on the crude oil, and is said to be only generated in the 
presence of hydrocyanic acid. It is easily extracted from the pasty mass, by 
dissolving out the lime and oxide of iron by h} r drochloric acid, and boiling 
the residue in alcohol. Benzoin forms colourless, transparent, brilliant, 
prismatic crystals, tasteless and inodorous; it melts at 248° (120°C), and 
distils without decomposition. Water, even at a boiling heat, dissolves but 
a small quantity of this body ; boiling alcohol takes it up in a larger propor- 
tion ; it dissolves in cold oil of vitriol, with violet colour. Benzoin contains 
C ]4 H 6 2 , or C^HjgO^ and is, consequently, an isomeric modification of bitter- 
almond oil. 

Benzile. — This curious compound is a product of the action of chlorine on 
benzoin ; the gas is conducted into the fused benzoin as long as hydrochloric 
acid continues to be evolved. It is likewise formed by treating benzoin with 
fuming nitric acid. The crude product is purified by solution in alcohol. It 
forms large, transparent, sulphur-yellow crystals, fusible at 200° (93° -3C), 
unaltered by distillation, and quite insoluble in water. It dissolves freely in 
alcohol, ether, and concentrated sulphuric acid, from which it is precipitated 
by water. Benzile is composed of C 14 H 5 2 , or C 28 Hi O 4 , and is therefore mo- 
meric with the radical of the benzoyl-series. 

Benzolic acid. — Benzoin and benzile dissolve with the violet tint in an 
alcoholic solution of caustic potassa ; by long boiling the liquid becomes 
colourless, and is then found to contain a salt of a peculiar acid, called the 
benzilic, which is easily obtained by adding hydrochloric acid to the filtered 
liquid, and leaving the whole to cool. Benzilic acid forms small, coloiirless, 
transparent crystals, slightly soluble in cold, more readily in boiling water ; 
it melts at 248° (120°C), and cannot be distilled without decomposition. It 
dissolves in cold concentrated sulphuric acid with a fine carmine-red colour. 
Benzilic acid contains C 2s H n 5 ,HO, or 2 eq. benzile and 1 eq. water. 

Benzoniteile. — When benzoate of ammonia is exposed to destructive dis- 
tillation, among other products a yellowish volatile oil makes its appearance, 
having exactly the odour of bitter-almond oil. It is heavier than water, 
slightly soluble in that liquid, boils at 376° (191°-1C), and contains C 14 H 5 N. 
It is benzoate of ammonia, — 4 eq. of water, (NH 4 0,C ]4 H 5 3 — 4HO=C 14 H 5 N,) 
and stands to this salt in the same relation as cyanogen to oxalate, hydro- 
cyanic acid to formate, and cyanide of methyl to acetate of ammonia. Ben- 
zonitrile likewise maybe viewed as a cyanide, when it becomes a member of 
the phenyl-series, C 14 H 5 N=C 12 H 5 C 2 N. 

Benzoyl. — Benzoate of copper by dry distillation cautiously conducted 
gives a residue containing salicylic and benzoic acids, and an oily distilled 
product which crystallizes on cooling. This substance possesses the odour 
of the geranium, melts at 158° (70°C), and contains C ]4 H 5 2 . It was dis- 
covered by Ettling, and subsequently studied by Stenhouse, and is evidently 
the radical of the benzoyl-series. By heating with hydrate of potassa it ig 
instantly converted into benzoic acid with disengagement of hydrogen. 

Benzimide. — This is a white, inodorous, shining, crystalline substance 

occasionally found in crude bitter-almond oil. It is insoluble in watei% and 

but slightly dissolved by boiling alcohol and ether. Oil of vitriol dissolves it 

with dark indigo-blue colour, becoming green by the addition of a little water. 

34- 



402 BITTER-ALMOND OIL AND ITS PRODUCTS. 

This reaction is characteristic. Benzimide contains C 28 H u N0 4 . It may be 
viewed as derived from an acid benzoate of ammonia by the separation of 4 
eq. of water. 

A great number of other compounds derived from bitter-almond oil, 
directly or indirectly, have been described by M. Laurent and others. Many 
of these contain sulphur, sulphuretted hydrogen and sulphide of ammonium 
being employed in their preparation. 

Hippueic acid. — This interesting substance is in some measure related to 
the benzoyl-compounds. It occurs, often in large quantity, in combination 
with potassa or soda, in the urine of horses, cows, and other graminivorous 
animals. It is prepared by evaporating in a water-bath perfectly fresh 
cow-urine to about a tenth of its volume, filtering from the deposit, and 
then mixing the liquid with excess of hydrochloric acid. Cow-urine fre- 
quently deposits hipp'uric acid without concentration, when mixed with a 
considerable quantity of hydrochloric acid, in which the acid is less soluble 
than in water. The brown crystalline mass which separates on cooling is 
dissolved in boiling water, and treated with a stream of chlorine gas until 
the liquid assumes a light amber colour, and begins to exhale the odour of 
that substance ; it is then filtered, and left to cool. The still impure acid is 
re-dissolved in water, neutralized with carbonate of soda, and boiled for a 
short time with animal charcoal ; the hot filtered solution is, lastly, decom- 
posed by hydrochloric acid. 

Hippuric acid in a pure state crystallizes in long, slender, milk-white, and 
exceedingly frangible square prisms, which have a slight bitter taste, fuse 
on the application of heat, and require for solution about 400 parts of cold 
water; it also dissolves in hot alcohol. It has an acid reaction, and forms 
salts with bases, many of which are crystallizable. Exposed to a high tem- 
nerature, hippuric acid undergoes decomposition, yielding benzoic acid, ben- 
zoate of ammonia, and a fragrant oily matter, with a coaly residue. With 
hot oil of vitriol, it gives off benzoic acid: boiling hydrochloric acid con- 
verts it into benzoic acid and glycocine (gelatin-sugar) which is described in 
the Section on Animal Chemistry. Hippuric acid contains C ]g H 8 N0 5 ,HO. 

The constitution of hippuric acid has been frequently discussed by che- 
mists. Very different views have been proposed. The most probable one 
is, that it is the amidogen compound of a peculiar acid — glycobenzoic acid. 
If hippuric acid be treated with nitrous acid, it undergoes the decomposition 
peculiar to amidogen-compouncls, which has been explained when treating of 
oxamide (page 343). A new non-nitrogenous acid is formed together with 
water and pure nitrogen C 18 II 8 N0 5 ,HO-j-N03=:C ]8 H 7 7 ,H04-HO-}-2N. 
Glycobenzoic acid is a crystalline substance, slightly soluble in water, but 
readily dissolved by alcohol and ether. It may be viewed as a conjugate 
acid, containing benzoic and glycolic acids — 2 eq. of water C ls H 7 7 ,HO 
= C 14 H 6 4 ,C 4 H 4 6 — 2HO. Under the influence of boiling water it splits 
indeed into benzoic and glycolic acids. Glycocine must be considered a- 
glycolamide NH 4 0,C 4 H 3 5 — 2HO = C 4 H 5 N0 4 , and this explains the conver- 
sion of hippuric acid into benzoic acid and glycocine. 

If, in the preparation of hippuric acid, the urine be in the slightest degree 
putrid, the hippuric acid is all destined during the evaporation, ammonia 
is disengaged in large quantity, and the liquid is then found to yield nothing 
but benzoic acid, not a trace of which can be discovered in the unaltered 
secretion. Complete putrefaction effects the same change ; benzoic acid 
might thus be procured to almost any extent. 

When benzoic acid is taken internally, it is rejected from the system in 
the state of hippuric acid, which is then found in the urine. 



BENZOYL-SERIES. 403 



HOMOLOGUES OE THE BENZOYL-SERIES. 

Tohiylic Acid, C ]6 H 7 3 ,HO. — This substance, which differs from benzoic 
acid by C 2 H 2 , has been lately discovered by Mr. Noad, who obtained it by 
the action of very dilute nitric acid upon cymol, a carbo-hydrogen occurring 
in cumin-oil. It is a substance exhibiting the closest analogy with benzoic 
acid both in its physical characters and in its chemical relations. Like 
benzoic acid, when treated with fuming nitric acid, it yields a nitro-acid, 
nitrotoluylic acid, C 16 H 6 NO 7 ,HO = C 10 (H 6 NO 4 )O 3 ,HO ; distilled with lime or 
baryta, it furnishes a hydro-carbon C 14 H g , homologous to benzol. The 
latter substance, which has received the name of toluol, is also obtained 
from other sources, especially from coal-tar and Tolu balsam. 

An acid of the formula C 18 H 9 3 ,HO, is not yet kjiown, but we may con- 
fidently expect that the progress of science will not fail to elicit this sub- 
stance ; even now we are acquainted with a hydrocarbon C 16 H 10 , homologous 
to benzol and toluol. This substance, which is called xylol, is found in 
wood-tar and coal-gas-naptha, and stands to the unknown acid Ci 8 H 9 3 HO 
in the same relation as benzol to benzoic acid. Should the above acid be 
discovered, we may with certainty predict that, when distilled with excess 
of lime, it will yield xylol. 

Cumic acid, C 20 H n O 3 , HO. — Another acid, homologous to benzoic acid, 
was discovered some time ago, by MM. Cahours and Gerhardt. It is formed 
by the oxydation of one of the constituents of cumin-oil, cuminol C 20 H 12 O 2 , 
which corresponds to oil of bitter almonds. It likewise yields a nitro-acid, 
nitro-curnic acid C 20 H, NO 7 ,HO = C 20 (H 10 NO 4 )O 3 ,HO, and when distilled is 
converted into cumol C 18 H 12 , a hydrocarbon, homologous to benzol, toluol, 
and xylol. 

Of the next series only the hydrocarbon is known. This is cymol C 20 H 14 , 
the substance which, as has been mentioned above, is the source of toluylio 
acid. 

The homology of these substances is clearly exhibited by the following 
table : — 

Hydrides. Acids. Hydrocarbons 

derived from the acid. 

Benzoyl-series C ]4 H 5 2 H C 14 H 5 3 ,HO C 12 H 6 

Toluyl-series " C 16 H 7 3 ,HO C 14 H 8 

Xylyl-series C 16 H 10 

Cumyl-series C 2(J H n 2 H C 20 H n O 3 ,HO C 1S H 12 

Cyniyl-series C 20 Hi 4 

This table shows that up to the present moment only the series of hydro- 
carbons is without a gap, while two acids and three hydrides remain to be 
discovered. 



SALICYL AND ITS COMPOUNDS. 



Salictn. — The leaves and young bark of the poplar, willow, and several 
other trees contain a peculiar cry stalliz able, bitter principle, called saltan, 
which in some respects resembles the vegeto-alkalis cinchonine and quinine, 
being said to have febrifuge properties. It differs essentially, however, from 
these bodies in being destitute of nitrogen, and in not forming salts with 
acids. Salicin may be prepared by exhausting the bark with boiling 
water, concentrating the solution to a small bulk, digesting the liquid with. 
powdered protoxide of lead, and then, after freeing the bolution from lead 
by a stream of sulphuretted-hydrogen gas, evaporating until the salicin crys- 



104 SALICYL. 

tallizes out on cooling. It is purified by treatment with animal charcoal and 
re-crystallization. 

Salicin forms small, white, silky needles, of intensely bitter taste, which 
have no alkaline reaction. It melts and decomposes by heat, burning with 
a bright flame, and leaving a residue of charcoal. It is soluble in 5-6 parts 
of cold water, and in a much smaller quantity when boiling hot. Oil of 
vitriol colours it deep red. The last experiments of M. Piria give for sali- 
cin the formula C 26 H ]8 14 . 

When salicin is distilled with a mixture of bichromate of potassa and sul- 
phuric acid, it yields, among other products, a yellow, sweet-scented oil, 
which is found to be identical with the volatile oil distilled from the flowers of the 
Spiroza ulmaria, or common meadow-sweet. This substance appears to be the 
hydride of a compound salt-radical, salicyl, containing C 14 H 5 4 ; it has the 
properties of a hydrogen-acid. 

Table of Salicy I- Compounds. 

Salicyl (symb. SI) C 14 H 5 4 

Hydrosalicylic acid C ]4 H 5 4 H 

Salicylide of potassium C 14 H 5 4 K 

Hydrochlorosalicylic acid C 14 (H 4 C1) 4 H 

'Hydriodosalicylic acid C 14 (H 4 I) 4 H 

Hydrobromosalicylic acid C 14 (H 4 Br)0 4 H 

Salicylic acid Ci 4 H 5 5 ,HO 

Hydrosalicylic acid ; salicylous acid ; artificial oil of meadow- 
sweet, S1H. — One part of salicin is dissolved in 10 of water, and mixed in a 
retort with 1 part of powdered bichromate of potassa and 2J parts of oil of 
vitriol diluted with 10 parts of water; gentle heat is applied, and after the 
cessation of the effervescence first produced, the mixture is distilled. The 
yellow oily product is separated from the water, and purified by rectifica- 
tion from chloride of calcium. It is thin, colourless, and transparent, but 
acquires a red tint by exposure to the air. Water dissolves a sensible quan- 
tity of this substance, acquiring the fragrant odour of the oil, and the cha- 
racteristic property of striking a deep violet colour with a salt of sesquioxide 
of iron, a property however which is also enjoyed by salicylic acid. Alcohol 
and ether dissolve it in all proportions. It has a density of 1-173, and boils 
at 385° (166°-1C), when heated alone. Hydrosalicylic acid decomposes the 
alkaline carbonates even in the cold ; it is acted upon with great energy by 
chlorine and bromine. By analysis it is found to contain C 14 H 6 4 , or the same 
elements as crystallized benzoic acid; and the density of its vapour is also 
the same, being 4-276. 

Salicylide of potassium, KS1. — This compound is easily prepared by 
mixing the oil with a strong solution of caustic potassa ; it separates, on agi- 
tation, as a yellow crystalline mass, which may be pressed between folds of 
blotting-paper, and re-crystallized from alcohol. It forms large, square, 
golden-yellow tables, which have a greasy feel, and dissolve very easily both 
iu water and alcohol; the solution has an alkaline reaction. When quite 
dry, the crystals are permanent in the air ; but in a humid state they soon 
become greenish, and eventually change to a black, soot-like substance, in- 
soluble in water, but dissolved by spirit and by solution of alkali, called 
vielanic acid. Acetate of potassa is formed at the same time. Melanic acid 
contains C 20 TT g O ]0 . The crystals of salicylide of potassium contain water 
•"vhich cannot be expelled without partial decomposition of the salt. 

Salicylide of ammonium, NH 4 S1, crystallizes in yellow needles which are 
quiclcly destroyed with production of ammonia and the hydride. Salicylide 
of ba-iuin, BaC 14 H 5 -f-2HO, forms fine yellow acicular ci'ystals, which are 



SALICYL. 405 

but slightly soluble in the cold. Salicylide of copper is a green insoluble 
powder, containing CuC 14 H 5 4 . 

Salicylide of copper by destructive distillation gives, among other products, 
hydride of salicyl and a solid body forming colourless prismatic crystals, 
fusible and volatile. It is insoluble in water, dissolved by alcohol and ether, 
and is unaffected by fusion with hydrate of potassa. Nitric acid converts it 
into anilic and picric acids. (See indigo). It contains C 14 H 3 3 , and is iso- 
meric with anhydrous benzoic acid. 

Chlorohydro-salicylic acid, C ]4 (H 4 C1)0 4 ,H. — Chlorine acts very strongly 
upon the hydride of salicyl ; the liquid becomes heated, and disengages large 
quantities of hydrochloric acid. The product is a slightly yellowish crys- 
talline mass, which, when dissolved in hot alcohol, yields colourless tabular 
crystals of the pure compound, having a pearly lustre. This substance is 
insoluble in water ; it dissolves freely in alcohol, ether,- and solutions of the 
fixed alkalis ; from the latter it is precipitated unaltered by the addition of 
an acid. It is not even decomposed by long ebullition with a concentrated 
solution of caustic potassa. Heated in a retort, it melts and volatilizes, con- 
densing in the cool part of the vessel in long, snow-white needles. The 
odour of this substance is peculiar and by no means agreeable, and its taste 
is hot and pungent. 

Chlorohydro-salicylic acid combines with the metallic oxides ; with potassa 
it forms small red crystalline scales, very soluble in water. The correspond- 
ing compound of barium, prepared from the foregoing, by double decompo- 
sition, is an insoluble crystalline, yellow powder, containing Ba C 14 (H 4 C1)0. 

Bromohydro-salicylic acid, C 14 (H 4 Br)0 4 ,H. — The bromide-compound is 
prepared by the direct action of bromine on the hydride of salicyl ; it crys- 
tallizes in small colourless needles, and very closely resembles in properties 
the chloride. The hydride of salicyl dissolves a large quantity of iodine, 
acquiring thereby a brown colour, but forming no combination ; the iodide 
may, however, be procured by distilling iodide of potassium with chlorohy- 
dro-salicylic acid. It sublimes as a blackish-brown fusible mass. 

Chloros amide. — The action of dry ammoniacal gas on pure chlorohydro- 
salicylic acid is very remarkable ; the gas is absorbed in large quantity, and 
a solid yellow, resinous-looking compound produced, which dissolves in 
boiling ether, and separates as the solution cools in fine yellow iridescent 
crystals ; this and a little water are the only products, not a trace of sal- 
ammoniac can be detected. Chlorosamide is nearly insoluble in water ; it 
dissolves without change in ether, and in absolute alcohol ; with hot rectified 
spirit it is partially decomposed, with disengagement of ammonia. Boiled 
with an acid, it yields an ammoniacal salt of the acid and chlorohydro-sali- 
cylic acid ; with an alkali, on the other hand, it gives free ammonia, while 
chlorohydro-salicylic acid remains dissolved. Chlorosamide contains C^ 
(Hi5Cl 8 )N 2 6 ; it is formed by the addition of 2 eq. of ammonia to 3 eq. of 
chlorohydro-salicylic acid, and the subsequent separation of 6 eq. of water 
A corresponding and very similar substance, bromosamide, is formed by the 
action of ammonia on bromohydro-salicylic acid. 

Saligekix. — This curious substance is a product of the decomposition of 
salicin under the influence of the emulsion or synaptase of sweet almonds ; 
it is also generated by the action of dilute acids. Ln both cases the salicin 
is resolved into saligenin and grape sugar. Saligenin forms colourless, na- 
creous scales, freely soluble in water, alcohol, and ether. It melts at 180° 
(82°C), and decomposes at a higher temperature. Dilute acids at a boiling 
heat convert it into a resinous-looking substance, C 14 H 6 2 , called saliretin. 
Many oxidizing agents, as chromic acid and oxide of silver, convert this sub- 
stance into hydride of salicyl : even platinum-black produces this effect. Itx 
aqueous solution gives a deep indigo-blue colour with salts of ses^uioxide oi 



406 SALICYL. 

iron. Saligenin contains C 14 H 8 4 . Hence the transformation of salicin is 
represented by the equations : — 

2C 26 If 18 14 -f8HO = C 24 n 28 2s - 2C M H 8 4 

Salicin. Grape-sugar. Saligenin. 

Salicin yields with chlorine substitution-compounds containing that ele- 
ment, -which are susceptible of decomposition by synaptase, with production 
of bodies termed chloro- and bichloromligcnin. Chlorosaligenin very closely 
resembles normal saligenin, and contains C 14 (H 7 C1)0 4 . Certain products, 
called by M. Piria helicin, helicoidin, and anilotic acid, are described as result- 
ing from the action of dilute nitric acid upon salicin. With strong acid at a 
high temperature niiro-salicylic acid (anilic acid) C J4 (H 4 N0 4 )O s ,HO, is pro- 
duced. 

Salicylic acid, S10,HO. — This compound is obtained by heating hydride 
of salicyl with excess of solid hydrate of potassa ; the mixture is at first 
brown, but afterwards becomes colourless ; hydrogen gas is disengaged 
during the reaction. On dissolving the melted mass in water, and adding a 
slight excess of hydrochloric acid, the salicylic acid separates in crystals, 
which are purified by re-solution in hot water. This substance very much 
resembles benzoic acid ; it is very feebly soluble in cold water, is dissolved 
in large quantities by alcohol and ether, and maybe sublimed with the utmost 
ease. It is charred and decomposed by hot oil of vitriol, and attacked with 
great violence by strong, heated nitric acid. Salicylic acid contains C 14 H 5 
5 ,HO. 

Salicylic acid can also be prepared with great ease by fusing salicin with 
excess of hydrate of potassa, and also by the action of a concentrated and 
hot solution of potassa upon the volatile oil of Gaultheria procumbens, which 
is the methyl-compound of this acid occurring in nature (see essential oils 
containing oxygen). When salicylic acid is mixed with powdered glass or 
sand and exposed to strong and sudden heat in a retort, it is almost entirely 
converted into carbonic acid and hydrate of phenyl, C 12 H 6 2 , a substance 
found in considerable proportion in coal-tar-naphta, — and the same change 
happens to many of its salts with even greater facility. 

Phlobidzin. — This is a substance bearing a great likeness to salicin, found 
in the root-rind of the apple and cherry-tree, and extracted by boiling al- 
cohol. It forms fine, colourless, silky needles, soluble in 1000 parts of cold 
water, but freely dissolved by that liquid when hot ; it is also soluble with- 
out difficulty in alcohol. It contains C 42 H 24 O 20 -{-4HO. Dilute acids convert 
phloridzin into grape-sugar and a crystallizable sweet substance called phlo- 
velin, C 20 H l4 Oi . 

2<Q«H w O M -f4HO) = C, 4 HA 

Phloridzin. Grape-sugar. rhloretin. 

Cumarin. — The odoriferous principle of the tonJca-bean. It may be often 
seen forming minute colourless crystals under the skin of the seed, and be- 
tween the cotyledons. It is best extracted by macerating the sliced beans 
in hot alcohol, and, after straining through cloth, distilling off the greater 
part of the spirit. The syrupy residue deposits on standing crystals of cu- 
marin, which must be purified by pressure from a fat oil which abounds in 
the beans, and then crystallized from the hot Avater. So obtained, cumarin 
forms slender, brilliant, colourless needles, fusible at 122° (50°C), and dis- 
tilling without decomposition at a higher temperature. It has a fragrant 
odour and burning taste ; it is very slightly soluble in cold water, mor« 



CINNAMYL AND ITS COMPOUNDS. 407 

freely in hot water, and also in alcohol. It is unaffected by dilute acids and 
alkalis, which merely dissolve it. Boiling nitric acid converts it into picric 
acid, and a hot concentrated solution of potassa into cumaric, and eventually 
into salicylic acid. Cumarin exists in several other plants, as the Meiilotu* 
officinalis, the Asperula adorata, and the Anthoxanlhum odoratum. According 
to M. Bleibtreu it contains C 18 H 6 4 . Cumaric acid is C 18 H 8 6 . 

CINNAMYL AND ITS COMPOUNDS. 

The essential oil of cinnamon seems to possess a constitution analogous to 
that of bitter-almond oil; it passes by oxidation into a volatile acid, the 
cinnamic, which resembles in the closest manner benzoic acid. The radical 
assumed iu these substances bears the name of cinnamyl ; it has not been 
isolated. 

Table of Cinnamyl- Compounds. 

Cinnamyl (symbol Ci) C 18 H 7 2 

Chloride of cinnamyl C 18 H 7 2 C1 

Hydride of cinnamyl; oil of cinnamon C 18 H 7 2 H • 

Hydrated oxide of cinnamyl; cinnamic acid C 1S H 7 2 0,H0 

Cinnamylic alcohol C IS H 9 0,HO 

Cinnamate of cinnamylic ether C 18 H 9 0,C 18 II 7 3 

Hydride of cinnamyl ; oil of cinnamon ; CiH.— Cinnamon of excellent 
quality is crushed, infused twelve hours in a saturated solution of common 
salt, and then the whole subjected to rapid distillation. "Water passes over, 
milky from essential oil, which after a time separates. It is collected and 
left for a short time in contact with chloride of calcium. This fragrant and 
costly substance has, like most of the volatile oils, a certain degree of solu- 
bility in water ; it is heavier than that liquid, and sinks to the bottom of the 
receiver in which the distilled products have been collected. It contains, 
according to M. Dumas, C 18 H 8 2 . 

Cinnamic acid, CiO,HO. — When pure oil of cinnamon is exposed to the 
air, or inclosed in a jar of oxygen, it is quickly converted by absorption of 
gas into a mass of white crystalline matter, which is hydrated cinnamic acid ; 
this is the only product. Cinnamic acid is found in Peruvian and Tolu bal- 
sams, associated with benzoic acid, and certain oily and resinous substances ; 
it may be procured by the following process in great abundance, and in a 
state of perfect purity. Old, hard Tolu balsam is reduced to powder and 
intimately mixed with an equal weight of hydrate of lime ; this mixture is 
boiled for some time in a large quantity of water, and filtered hot. On cool- 
ing, cinnamate of lime crystallizes out, while benzoate of lime remains in 
solution. The impure salt is re-dissolved in boiling water, digested with 
auimal charcoal, and, after filtration, suffered to crystallize. The crystals 
are drained and pressed, once more dissolved in hot water, and an excess of 
hydrochloric acid being added, the whole is allowed to cool ; the pure cin- 
namic acid separates in small plates or needle-formed crystals of perfect 
whiteness. From the original mother-liquor much benzoic acid can be pro- 
cured. 

The crystals of cinnamic acid are smaller and less distinct than those of 
benzoic acid, which in most respects it very closely resembles. It melts at 
248° (120°C), and enters into ebullition and distils without change at 560° 
(293°-3C); the vapour is pungent and irritating. Cinnamic acid is much 
less soluble, both in hot and cold water, than benzoic ; a hot saturated solu- 
tion becomes on cooling a soft-solid mass of small nacreous crystals. It 
dissolves with perfect ease in alcohol. Boiling nitric acid decomposes cm- 



408 CINNAMYL AND ITS COMPOUNDS. 

namic acid with great energy, and with production of copious red fumes ; 
bitter almond-oil distils over, and benzoic acid remains in the retort in which 
the experiment is made. When cinnamic acid is heated in a retort with a 
mixture of strong solution of bichromate of potassa and oil of vitriol, it is 
almost instantly converted into benzoic acid, which afterwards distils over 
with the vapour of water: the odour of bitter-almond-oil is at the same 
time very perceptible. The action of chlorine is different ; no benzoic acid 
is formed, but other products, which have not been perfectly studied. 

Cinnamic acid forms with bases a variety of salts which are very similar 
to the benzoates. The crystallized acid contains C ls H 7 3 ,HO. "When dis- 
tilled with an excess of lime or baryta, cinnamic acid undergoes a decompo- 
sition analogous to that of benzoic acid ; an oily liquid cinnamol C ]6 H 8 distils 
over, whilst a carbonate of the alkaline earth remains behind, C lg H 8 4 -(- 
2BaO==2(BaO,C0 2 )-{-C 18 H 6 . This oil is also found in liquid storax, and is 
frequently described by the term styrol. (See resins and balsams.) 

Chlorocinnose. — This is the ultimate product, of the action of chlorine on 
oil of cinnamon by the aid of heat. When purified by crystallization from 
alcohol, it forms brilliant, colourless needles, fusible, and susceptible of vola- 
tilization without change. It is not affected by boiling oil of vitriol, and 
may be distilled without decomposition in a current of ammoniacal gas. 
Chlorocinnose contains C 18 H 4 C1 4 2 ; it is formed by the substitution in the 
oil of cinnamon of 4 eq. of chlorine for 4 eq. of hydrogen. The true chloride 
of cinnamyl, Ci CI, seems to be first formed in considerable quantity, and 
subsequently decomposed by the continued action of the chlorine ; it has not 
been separated in a pure state ; it appears as a very thin, fluid oil, convertible 
into a crystalline mass by strong solution of potassa. 

AVhen cinnamon-oil is treated with hot nitric acid, it undergoes decompo- 
sition, being converted into hydride of benzoyl and benzoic acid. With a 
boiling solution of chloride of lime the same thing happens, a benzoate of the 
base being generated. If the oil be heated with solution of caustic potassa 
it remains unaffected ; with the solid hydrate, however, it disengages pure 
hydrogen, and forms a potassa-salt, which appears to be the cinnamate. 
When brought into contact with cold concentrated nitric acid, a crystalline, 
yellowish, scaly compound is obtained, "which is decomposed by water with 
separation of the oil. With ammonia a solid substance is produced, which 
also appears to be a direct compound of the two bodies. 

Two varieties of oil of cinnamon are met with in commerce of very unequal 
value, viz. that of China, and that of Ceylon ; the former being considered 
the best: both are, however, evidently impure. The pure oil maybe ex- 
tracted from them by an addition of cold, strong nitric acid ; the crystalline 
matter which forms after the lapse of a few hours, separated and decomposed 
by water, yields ure hydride of cinnamyl. 



There can be no doubt that the cinnamic acid in Tolu and Peru balsams 
is gradually formed by the oxidation of a substance very closely related to 
the alcohols. When these balsams are first imported they are nearly fluid, 
but gradually acquire consistence by keeping. By the aid of an alcoholic 
solution of potassa, a compound, sometimes oily, sometimes solid, may be 
separated from these balsams, which cannot be distilled without partial de- 
composition. This compound, described respectively under the name of 
cinnamein (when oily), and s/yracin (when solid), when distilled with hydrate 
of potassa, is converted into cinnamic acid and a neutral substance, which 
likewise occurs in an oily and crystalline modification, and has been called, 
respectively, peruvin and styrone. These substances are related to each other 
in a very remarkable manner. Peruvin may be viewed as the alcohol of 



CINNAMYL AND ITS COMPOUNDS. 



409 



cinnamic acid, -when cinnamein becomes the compound ether consisting of 
alcohol and cinnamic acid. This relation will become obvious by the fol- 
lowing formulas : — 



Ethyl-series. 

Alcohol C 4 F 5 0,HO 

Acetic acid C 4 H 3 3 ,HO 

Acetic ether C 4 H 5 0,C 4 H 3 3 



Cinnamyl-series. 



Cinnamic acid C 18 H 7 3 ,HO 

Cinnamein C 18 H 9 0,C 18 II 7 3 



When treated with oxidizing agents, peruvin yields cinnamic add, or its 
products of decomposition, oil of bitter-almonds and benzoic acid. 



410 VEGETABLE ACIDS. 



SECTION III. 
VEGETABLE ACIDS. 



The vegetable acids constitute a very natural and important family or 
group of compounds, many ot which possess the property of acidity, *. e, 
acid reaction to litmus paper, and power of forming stable, neutral, and often 
cr.ystallizable compounds with bases, to an extent comparable with that of 
the mineral acids. Some of these bodies are very widely diffused through 
the vegetable kingdom ; others are of much more limited occurrence, being 
found in some few particular plants only, and very frequently in combina- 
tion with organic alkaline bases, in conjunction with which certain of them 
will be found described. Many of the vegetable acids are polybasic ; and it 
is remarkable that in the new products, or pyro-acids, to which they often 
give rise under the influence of heat, this character is usually lost. 

The particular acids now to be described are for the most part of extensive 
and general occurrence ; mention will be made of some of the rarer ones in 
connection with their respective sources. 

Table of Vegetable Acids. 

Tartaric acid C 8 H 4 O 10 ,2Ht, 

Racemic acid C 8 H 4 O 10 ,2HO 

Citric acid C 12 H 5 0„,3HO 

Aconitic, or equisetic acid C 4 H 3 ,HO 

Malic acid...* C 8 H 4 8 ,2HO 

Fumaric acid C 4 H 3 ,HO 

Tannic acid C 19 H 5 9 .3HO 

Gallic acid C 7 H 3 ,2HO 

Tartabic acid. — This is the acid of grapes, of tamarinds, of the pine- 
apple, and of several other fruits, in which it occurs in the state of an acid 
potassa-salt; tartrate of lime is also occasionally met with. The tartaric 
acid of commerce is wholly prepared from the tartar or argol, an impure acid 
tartrate of potassa, deposited from wine, or rather grape-juice, in the act of 
fermentation. This substance is purified by solution in hot water, the use 
of a little pipe-clay, and animal charcoal to remove the colouring-matter of 
the wine, and subsequent crystallization ; it then constitutes cream of tartar , 
and serves' for the prepai\ation of the acid. The salt is dissolved in boiling 
water, and powdered chalk added as long as effervescence is excited, or the 
liquid exhibits an acid reaction; tartrate of lime and neutral tartrate of 
potassa result ; the latter is separated from the former, which is insoluble, 
by filtration. The solution of tartrate of potassa is then mixed with excess 
of chloride of calcium, which throws down all the remaining acid in the form 
of lime-salt; this is washed, added to the former portion, and then the 
whole digested with a sufficient quantity of dilute sulphuric acid to with- 
draw the base and liberate the organic acid. The filtered solution is cau- 
tiously evaporated to a syrupy consistence and placed to crystallize in a wa^m 
situation. 



VEGETABLE ACIDS. 411 

Tartaric acid forms colourless, transparent crystals, often of large size, 
which have the figure of an oblique rhombic prism more or. less modified; 
these are permanent in the air, and inodorous ; they dissolve with great 
facility in water, both hot and cold, and are also soluble in alcohol. The 
solution reddens litmus strongly, and has a pure acid taste. The aqueous 
solution, as has been mentioned (page 76), possesses right-handed polariza- 
tion. This solution is gradually spoiled by keeping. Tartaric acid is 
bibasic; the crystals contain C 8 H 4 O I0 ,2HO. This substance is consumed in 
large quantities by the calico-printer, being employed to evolve chlorine from 
solution of bleaching-powder in the production of white or discharged pat- 
terns upon a coloured ground. 

Tartrate of potassa. Neutral tartrate ; soluble tartar ; 2KO, 
C 8 H 4 O 10 . — The neutral salt may be procured by neutrarizing cream of tartar 
with chalk, as in the preparation of the acid, or by adding carbonate of 
potassa to cream of tartar to saturation ; it is very soluble, and crystallizes 
with difficulty in right rhombic prisms, which are permanent in the air, and 
have a bitter, saline taste. 

Acid tartrate of potassa; cream of tartar; KO,HO,C 8 H 4 O, . — The 
origin and mode of preparation of this substance have been already de- 
scribed. It forms small transparent or translucent prismatic crystals, irre- 
gularly grouped together, which grit between the teeth. It dissolves pretty 
freely in boiling water, but the greater part separates as the solution cools, 
leaving about ^ or less dissolved in the cold liquid. The salt has an acid 
reaction, and a sour taste. "When exposed to heat in a close vessel, it is de- 
composed with evolution of inflammable gas, leaving a mixture of finely- 
divided charcoal and pure carbonate of potassa, from which the latter may 
be extracted by water. Cream of tartar is almost always produced when 
tartaric acid in excess is added to a moderately strong solution of a potassa- 
salt, and the whole agitated. 

Tartratts of soda. — Two compounds of tartaric acid with soda are 
known: a neutral salt, 2NaO,C 8 H 4 O 10 -f 4HO ; and an acid salt, NaO,HO, 
C 8 H 4 Oi -f-2HO. Both are easily soluble in water, and crystallize. Tartaric 
acid and bicarbonate of soda form the ordinary effervescing draughts. 

Tartrate of potassa and soda ; Rochelle or seignette salt ; KO, 
NaO,C 8 H 4 O 10 -(-10HO. — This beautiful salt is made by neutralizing with car- 
bonate of soda a hot solution of cream of tartar, and evaporating to the 
consistence of thin syrup. It separates in large, transparent, prismatic 
crystals, the faces of which are unequally developed ; these effloresce slightly 
in the air, and dissolve in 1| parts of cold water. Acids precipitate cream 
of tartar from the solution. Rochelle salt has a mild, saline taste, and is 
used as a purgative. 

Tartrates of ammonia. — The neutral tartrate is a soluble and efflorescent 
salt, containing 2NH 4 O,C 8 H 4 O 10 -J-2HO. The acid tartrate, NH 4 O,HO,C 8 H 4 O 10 , 
closely resembles ordinary cream of tartar. A salt corresponding to Rochelle 
salt also exists, having oxide of ammonia in place of soda. 

The tartrates of lime, baryta, slronlia, magnesia, and of the oxides of most 
of the metals proper, are insoluble, or nearly so, in water. 

Tartrate of antimony and potassa; tartar emetic. — This salt is easily 
made by boiling teroxide of antimony in solution of cream of tartar ; it is 
deposited from a hot and concentrated solution in crystals derived from au 
octahedron with rhombic base, which dissolve without decomposition in 15 
parts of cold, and 3 of boiling water, and have an acrid and extremely dis- 
agreeable taste. The solution is incompatible with, and decomposed by, both 
acids and alkalis ; the former throw down a mixture of cream of tartar and 
teroxide of antimony, and the latter, the teroxide, which is again dissolved 
by great excess of the reagent. Sulphuretted hydrogen separates all the 



412 VEGETABLE ACIDS. 

antimony in the state of tersulphide. Heated in a dry state on charcoal 
before the blowpipe, it yields a globule of metallic antimony. The crystals 
contain KO,SbO 3 ,C 8 H 4 Oi -f2HO. 1 



An analogous compound containing arsenious acid (As0 3 ) in place of ter- 
oxide of antimony has been described. It has the same crystalline form as 
tartar-emetic. 

A solution of tartaric acid dissolves hydrated sesquioxide of iron in large 
quantity, forming a brown liquid which has an acid reaction, and dries up by 
gentle heat to a brown, transparent, glassy substance, destitute of all traces 
of crystallization. It is very soluble in water, and the solution is not pre- 
cipitated by alkalis, fixed or volatile. Indeed, tartaric acid added in sufficient 
quantity to a solution of sesquioxide of iron or alumina, entirely prevents 
the precipitation of the bases by excess of ammonia. Tartrate and ammoni- 
acal tartrate of iron are used in medicine, these compounds having a less 
disagreeable taste than most of the iron-preparations. 

Solution of tartaric acid gives white precipitates with lime- and baryta- 
water, and with acetate of lead, which dissolve in excess of the acid ; with 
neutral salts of lime and baryta no change is produced. The effect on solu- 
tion of potassa-salts has been already noticed. 



Action of heat on tartaric acid. — When crystallized tartaric acid is 
exposed to a temperature of 400° (204° -5C) or thereabouts, it melts, loses 
water, and passes through three different modifications, called in succession 
tartralic, tartrelic, and anhydrous tartaric acid. The two first are soluble in 
water, and form salts, which have properties completely different from those 
of ordinary tartaric acid. The third substance, or anhydrous acid, is a white 
insoluble powder. All three, in contact with water, slowly pass into common 
tartaric acid. Their composition is thus expressed : — 

Ordinary tartaric acid C 8 H 4 O, ,2HO 

Tartralic acid 2C 8 H 4 O 10 ,3HO 

Tartrelic acid C s H 4 O 10 ,HO 

Anhydrous acid C 8 H 4 O 10 

The analogy borne by these bodies to the several modifications of phos- 
phoric acid will be at once evident. 

Pyrotartaric acid. — When crystallized tartaric acid is subjected to 
destructive distillation, a heavy acid liquid containing this substance passes 
over, accompanied by a large quantity of carbonic acid ; in the retort is left 
a semi-fluid black mass, which, by farther heating, gives combustible gases, 
an empyreumatic oil, and a residue of charcoal. The distilled product 
exhales a powerful odour of acetic acid, and is with great difficulty purified. 
Pyrotartaric acid forms a series of salts, and an ether ; it is supposed to con- 
tain C 6 H 3 5 ,HO. A second pyro-acid sometimes separates in crystals from the 
preceding compound, and may be obtained in larger quantity by the destruc- 
tive distillation of cream of tartar ; it is composed of C 5 H 3 3 ,HO. 

When tartaric acid is heated to 400° (204° -5C) with excess of hydrate of 
potassa, it is resolved without charring or secondary decomposition into oxa- 

1 According to Dumas, KO.SbOa.CsT^Oio+IIO. Dried at 212° (100°C), an equivalent of 
water is losC and at 42S°(220°C). two additional equivalents, Leaving the compound KOjSbOs, 
Oll 2 08, which can no longer contain ordinary tartaric acid. Nevertheless, when dissolved in 
water, the crystals again take up the elements of water and reproduce the original salt. 



VEGETABLE ACIDS. 413 

lie and acetic acids, which remain in union with the base, and only undergo 
decomposition at a much higher temperature. 

Racemic acid ; paratartaric acid. — The grapes cultivated in certain 
districts of the Upper Rhine, and also in the Vosges, in France, contain, in 
association with tartaric acid, another and peculiar acid body, to which the 
term racemic acid is given ; it is rather less soluble than tartaric acid, and 
separates first from the solution of that substance. Between these two acids, 
however, the greatest possible resemblance exists ; they have exactly the 
same composition, and yield, when exposed to heat, the same products ; the 
salts of racemic acid correspond, in the closest manner, with the tartrates. 
A solution of this acid precipitates a neutral salt of lime, which is not the 
case with tartaric acid. A solution of racemic acid does not rotate the plane 
of polarization. 

Racemic acid has been lately the subject of some exceedingly interesting 
researches by M. Pasteur, which have thrown much light upon the relation 
of this acid to tartaric acid. If racemic acid be saturated with potassa, or 
soda, or with most other bases, crystals are obtained, which are identical in 
form and physical properties. By saturating racemic acid, however, with 
two bases, by forming, for instance, compounds corresponding to Rochelle- 
salt, which contain potassa and soda or ammonia and soda, and allowing the 
solution to crystallize slowly, two varieties of crystals are produced, which 
may be distinguished by their form, namely, as the image and the reflection 
of the image, or as right-handed and left-handed. If the two kinds of 
crystals are carefully selected and separately crystallized, in each case crys- 
tals of the one variety only are deposited. The composition, the specific 
gravity, and, in fact, most of the physical properties of these two varieties 
of racemate of potassa and soda, are invariably the same. They differ, how- 
ever, somewhat in their chemical characters, and especially in one point, 
they rotate the plane of polarization in opposite directions. (See page 76.) 
M. Pasteur assumes in the two varieties of crystals the existence of two 
modifications of the same acid, which he distinguishes, according as the salts 
possess right- or left-handed polarization, by the terms dcxtroracernic and 
levoracemic acids. These acids can be separated by converting the above 
compounds into lead- or baryta-salts, and decomposing them by means of 
sulphuric acid. In this manner two crystalline acids are obtained, identical 
in every respect excepting in their deportment with polarized light, and in 
their crystals behaving as image and reflection. It is very probable, not to 
say certain, that dextroracemic acid is nothing but common tartaric acid. 
A mixture of equal parts of the two acids has no longer the slightest effect 
on polarized light, and exhibits in every respect the deportment of racemic 
acid. 

Citric acid. — Citric acid is obtained in large quantity from the juice of 
limes and lemons ; it is found in many other fruits, as in gooseberries, cur- 
rants, &c, in conjunction with another acid, the malic. In the preparation 
of this acid, the juice is allowed to ferment a short time, in order that muci- 
lage and other impurities may separate and subside ; the clear liquor is then 
carefully saturated with chalk, which forms, with the citric acid, an insoluble 
compound. This is thoroughly washed, decomposed by the proper quantity 
of sulphuric acid, diluted with water, and the filtered solution evaporated to 
a small bulk, and left to crystallize. The product is drained from the mother- 
liquor, re-dissolved, digested with animal charcoal, and again concentrated 
to the crystallizing-point. Citric acid forms colourless, prismatic crystals, 
which have a pure and agreeable acid taste ; they dissolve, with great ease, 
in both hot and cold water ; the solution strongly reddens litmus, and, when 
long kept, is subject to spontaneous change. 

Citric acid is tribasic; its formula in the gently dried and anhydrous silver 
35* 



414 VEGETABLE ACIDS. 

salt is C 12 H 5 O n . The hydrated acid crystallizes with two different quantities 
of water, assuming two different forms. The crystals, which separate by 
spontaneous evaporation from a cold saturated solution, contain C 12 H 5 O n , 
3HO-J-2IIO, the last being water of crystallization ; while, on the other hand, 
those which are deposited from a hot solution contain but 4 equivalents of 
water altogether, three of which are basic. Citric acid is entirely decomposed 
when heated with sulphuric and nitric acids; the latter converts it into oxalic 
acid. Caustic potassa, at a high temperature, resolves it into acetic and 
oxalic acids. 1 When subjected to the action of chlorine, the alkaline citrates 
yield among other products chloroform. 

The citrates are very numerous, the acid forming, like ordinary phosphoric 
acid, three classes of salts, which contain respectively 3 eq. of a metallic 
oxide, 2 eq. of oxide and 1 eq. of basic water, and 1 eq. oxide and 2 eq. basic 
water, besides true basic salts, in which the water of crystallization is perhaps 
replaced by a metallic oxide. 

The citrates of the alkalis are soluble and crystallizable with greater or 
less facility ; those of baryta, slrontia, lime, lead, and silver are insoluble. 

Citric acid resembles tartaric acid in its relations to sesquioxide of iron ; 
it prevents the precipitation of that substance by excess of ammonia. The 
citrate, obtained by dissolving the hydrated sesquioxide in solution of citric 
acid, dries up to a pale-brown, transparent, amorphous mass, which is not 
very soluble in water ; an addition of ammonia increases the solubility. 
Citrate and ammonio-citrate of iron are elegant medicinal preparations. Very 
little is known respecting the composition of these curious compounds; the 
absence of crystallization is a great bar to inquiry. 

Citric acid is sometimes adulterated with tartaric ; the fraud is easily 
detected by dissolving the acid in a little cold water, and adding to the solu- 
tion a small quantity of acetate of potassa. If tartaric acid be present, a 
white crystalline precipitate of cream of tartar will be produced on agitation. 

Aconitic, or equisetic acid. — When crystallized citric acid is heated in 
a retort until it begins to become coloured, and to undergo decomposition, 
and the fused, glassy product, after cooling, dissolved in water, an acid is 
obtained, differing completely in properties from citric acid, but identical 
with an acid extracted from the Aconitum. napellus and the Equisetum fluviatile. 
Aconitic acid forms a white, confusedly-crystalline mass, permanent in the 
air, and very soluble in water, alcohol, and ether; the solution has an acid 
and astringent taste. The salts of aconitic acid possess but little interest; 
that of baryta forms an insoluble gelatinous mass; aconitate of lime, which 
has a certain degree of solubility, is found abundantly in the expressed juice 
of the monkshood, and aconitate of magnesia in that of the equisetum. 

Hydrated aconitic acid contains C 4 HO s ,HO; it is formed in the artificial 
process above described, by the breaking up of 1 eq. of hydrated citric acid, 
C, 2 H 8 14 , into 2 eq. of water and 3 eq. of hydrated aconitic acid. There 
are, however, invariably many secondary products formed, such as acetone, 
carbonic oxide, and carbonic acid. The farther action of heat upon aconitic 
acid gives rise to several new acids, especially citraconic and itaconic acids, 
both expressed by the formula C 5 II 2 3 ,HO. The limits of this elementary 
work will not permit us to enter into a description of these farther products 
of decomposition. 

Malic acid. — This is the acid of apples, pears, and various other fruits; 
it is often associated, as already observed, with citric acid. An excellent 

1 The easy resolution of tartaric and citric acids into a mixture of oxalic and acetic acids 
by the action of heat, aided by the presence of a powerful base, has led to the idea of the pos- 
sible pre-existence of these last-named bodies in the two vegetable a< ids. -which may thus he 
compounded of two acids of simpler constitution, forming coupled or conjugate acids, of which 
peroral have heen supposed to exist. These views, although sometimes useful, are not at 
present supported by evidence of great importance. 



VEGETABLE ACIDS. 415 

process for preparing the acid in question is that of Mr. Everitt, "who has 
demonstrated its existence, in great quantity, in the juice of the common 
garden rhubarb ; it is accompanied by acid oxalate of potassa. The rhubarb 
6talks are peeled, and ground or grated to pulp, which is subjected to pres- 
sure. The juice is heated to the boiling-point, neutralized with carbonate 
of potassa, and mixed with acetate of lime ; insoluble oxalate of lime falls, 
which is removed by filtration. To the clear and nearly colourless liquid, 
solution of acetate of lead is added as long as a precipitate continues to be 
produced. The malate of lead is collected on a filter, washed, diffused 
through water, and decomposed by sulphuretted hydrogen. 1 The filtered 
liquid is carefully evaporated to the consistence of syrup, and left in a dry 
atmosphere until it becomes converted into a solid and somewhat crystalline 
mass of malic acid : regular crystals have not been obtained. From the 
berries of the mountain-ash (sorbus aucuparia) in which malic acid is like- 
wise present in considerable quantity, especially at the time they commence 
to. ripen, the acid may be prepared by the same process. 

Malic acid is bibasic, its formula being C 8 H 4 8 ,2HO ; it forms a variety 
of salts, some of which are neutral, others acid. In the presence of fer- 
menting substances, especially of putrifying casein, it is itself decomposed, 
yielding succinic, acetic, and carbonic acid. 

3(C 8 H 4 8 ,2HO) = 2(C 8 H 4 6 ,2HO) + C 4 H 3 3 ,HO-f 4C0 2 +2HO. ' 

Malic acid. Succinic acid. Acetic acid. 

Sometimes also butyric acid and hydrogen are observed among the products 
of this decomposition. Malic acid is colourless, slightly deliquescent, and 
very soluble in water; alcohol also dissolves it. The aqueous solution has 
an agreeable acid taste ; it becomes mouldy, and spoils by keeping. The 
most characteristic of the malates are the acid malate of ammonia, NH 4 0,HO, 
C g H 4 O g , which crystallizes remarkably well, and the malate of lead, which is 
insoluble in pure water, but dissolves, to a considerable extent, in warm 
dilute acid, and separates, on cooling, in brilliant, silvery crystals which con- 
tain water. The acid may, by this feature, be distinguished. The acid ma- 
late of lime, CaO,HO,C 8 H 4 8 -f-6HO, is also a very beautiful salt, freely solu- 
ble in warm water. It is prepared by dissolving the sparingly soluble neutral 
malate of lime in hot dilute nitric acid, and leaving the solution to cool. 

Recent researches of M. Piria have established a most intimate relation 
between malic acid and two substances — asparagin and aspartic acid, which 
will be described in one of the succeeding sections. Th^se compounds may 
be viewed as malamide and malamic acid, analogous to oxamide and oxamic 
acid. 

Oxalic acid a . . C 4 6 ,2HO Malic acid . . C s H 4 8 ,2HO 

Neutral oxalate of "» n ^ ovn ~ f Neutral malate of) n tt ~ OATrr ^ 

ammonia . . jtA^H.O j ammonia . . }C 8 H 4 8 ,2NE 4 

Oxamide. . .}c 4 H 4 N 2 4 { ~ de ' ^ } C 8 H 8 N 2 6 

B mo°nia lat . e °f ?" } C 4 6 ,HO,NH 4 { *™ e . of am " } C 8 H 4 8 ,HO,NII 4 
Oxamic acid . 1 C.H.N 0„HO \ Malamio acid ; as- \ c H v , fH 



C 4 H 2 N 5 ,H0 { Malamio a ?* d ; as " ) C,H 4 NO. 
4 2 5 ' L partic acid / R 4 ' 



1 If the acid be required pure, crystallized malate of lead must be used, the freshly preci- 
pitated salt invariably carrying down a quantity of lime, which cannot be removed by simple 
■washing. 

3 We have here doubled the formula of oxalic acid, when it becomes bibasic, like malic acid 
There are, in fact, many features in the history of oxalic acid, which render it probable tha 
it is bibasic. In the text we have still retained the generally received formula. 



416 VEGETABLE ACIDS. 

Hitherto neither asparagin nor aspartic acid have been actually obtained 
from malic acid. On the contrary, these substances are converted with the 
greatest facility into malic acid. On passing a current of nitrous acid into 
a solution of asparagin or aspartic acid, pure nitrogen is evolved, malic being 
liberated. 

C s H 8 N 2 6 + 2N0 3 = C s H 4 8 ,2HO -f 2HO -f 4N 
Asparagin. Malic acid. 

Fumaric and maleic acids. — If malic acid be heated in a small retort, 
nearly filled, it melts, emits water, and enters into ebullition ; a volatile 
acid passes over, which dissolves in the water of the receiver. After a time, 
small solid, crystalline scales make their appearance in the boiling liquid, 
and increase in quantity, until the whole becomes solid. The process may 
now be interrupted, and the contents of the retort, after cooling, treated 
with cold water ; unaltered malic acid is dissolved out, and the new sub- 
stance, having a smaller degree of solubility, is left behind; it is called 
fumaric acid, from its identity with an acid extracted from the common 
fumitory. 

Fumaric acid forms small, white, crystalline laminae, which dissolve freely 
in hot water and alcohol, but require for that purpose about 200 parts of 
cold water ; it is unchanged by hot nitric acid. When heated in a current 
of air it sublimes, but in a retort undergoes decomposition. This is a 
phenomenon often observed in organic bodies of small volatility. Fumaric 
acid forms salts, which have been examined by M. Rieckher, and an ether, 
which, by the action of ammonia, yields a white, amorphous, insoluble 
powder, called fumar amide, corresponding in properties and constitution 
with oxamide. Hydrated fumaric acid contains C 4 H0 3 ,HO ; hence it is 
isomeric with aconitic acid. 

The volatile acid produced simultaneously with the fumaric acid is called 
maleic acid ; it may be obtained in crystals by evaporation in a warm place. 
It is very soluble in water, alcohol, and ether ; it has a strong acid taste 
and reaction, and is convertible by heat into fumaric acid. Hydrated maleic 
acid contains C 8 H 2 6 ,2HO. Maleic and fumaric acids are thus seen to have 
precisely the same composition ; they are formed by the separation of 2 eq. 
of water from hydrated malic acid. 

Tannic and gallic acids. — These are substances in which the acid 
character is much less strongly marked than in the preceding bodies ; they 
constitute the astringent principles of plants, and are widely diffused, in 
one form or other, through the vegetable kingdom. It is possible that there 
may be several distinct modifications of tannic acid, which differ among 
themselves in some particulars. The astringent principle of oak-bark and 
nut-galls, for example, is found to precipitate salts of sesquioxide of iron 
bluish-black, while that from the leaves ef the sumach and tea-plant, as 
well as infusions of the substances known in commerce under the name of 
Mno and catechu, are remarkable for giving, under similar circumstances, 
precipitates which have a tint of green. The colour of a precipitate is, 
however, too much influenced by external causes to be relied upon as a 
proof of essential difference. Unfortunately, the tannic acid or acids refuse 
to crystallize ; one most valuable test of individuality is therefore lost. 

After the reaction with salts of sesquioxide of iron, the most character- 
istic feature of tannic acid and the other astringent infusions refei-red to, is 
that of forming insoluble compounds with a great variety of organic, and 
especially animal substances, as solutions of starch and gelatin, solid mus- 
cular fibre and skin, &c, which then acquire he property of resisting putre- 



VEGETABLE ACIDS. 



417 



Fig. 172. 



faction ; it 1b on this principle that leather is manufactured. Gallic acid, on 
the contrary, is useless in the operation of tanning. 

Tannic Acid of the Oak. — This substance may be prepared by the elegant 
and happy method of M. Pelouze, from nut-galls, which are 
excrescences produced on the leaves of a species of oak, the 
Quercus infectoria, by the puncture of an insect. A glass 
vessel, having somewhat the figure of that represented in the 
margin, fig. 172, is loosely stopped at its lower extremity by 
a bit of cotton wool, and half or two-thirds filled with pow- 
dered Aleppo-galls. Ether, prepared in the usual manner by 
rectification, and containing, as it invariably does, a little 
water, is then poured upon the powder, and the vessel loosely 
stopped. The liquid, which after some time collects in the 
receiver below, consists of two distinct strata ; the lowest, 
which is almost colourless, is a very strong solution of nearly 
pure tannic acid in water; the upper consists of ether holding 
in solution gallic acid, colouring matter, and other impurities. 
The carefully-separated heavy liquid is placed to evaporate 
over a surface of oil of vitriol in the vacuum of the air-pump. 
Tannic acid, or tannin, thus obtained, forms a slightly yellowish, 
friable, porous mass, without the slightest tendency to crystal- 
lization. It is very soluble in water, less so in alcohol, and 
very slightly soluble in ether. It reddens litmus, and pos- 
sesses a pure astringent taste without bitterness. 

A strong solution of this substance mixed with mineral acids 
gives rise to precipitates, which consist of combinations of the 
tannic acid with the acids in question ; these compounds are 
freely soluble in pure water, but scarcely so in acid solutions. 
Tannic acid precipitates albumin, gelatin, salts of the vegeto- 
alkalis, and several other substances ; it forms soluble com- 
pounds with the alkalis, which, if excess of base be present, rapidly attract 
oxygen, and become brown by destruction of the acid ; the tannates of 
baryta, strontia, and lime are sparingly soluble, and those of the oxides of 
lead and antimony insoluble. Salts of protoxide of iron are unchanged by 
solution of tannic acid ; salts of the sesquioxide, on the contrary, give with 
it a deep bluish-black precipitate, which is the basis of writing-ink ; hence 
the value of an infusion of tincture of nut-galls as a test for the presence 
of that metal. The action of acids xipon tannic acid gives rise to the for- 
mation of gallic acid, which will be presently described, with simultaneous 
separation of grape-sugar. Hence tannic acid would appear to be a conju- 
gated sugar-compound. 

Tannic acid, carefully dried, contains CjgE^Og-f-SHO. 1 

Tannic acid, closely resembling that obtained from galls, may be extracted 
by cold water from catechu; hot water dissolves out a substance having 
feeble acid properties, termed catechin. This latter compound, when pure, 
crystallizes in fine colourless needles, which melt when heated, and dissolve 
very freely in boiling water, but scarcely at all in the cold. Catechin dis- 
solves also in hot alcohol and ether. The aqueous solution acquires a red 
tint by exposure to air, and precipitates acetate of lead and corrosive subli- 
mate white, reduces nitrate of silver on the addition of ammonia, but fails 
to form insoluble compounds with gelatin, starch, and the vegeto-alkalis. It 



* This formula is scarcely established beyond a doubt. M. Strecker, who has observed the 
formation of sugar from tannic acid, represents this substance by the formula C40IH6O26, ami 
its change under the influence of acids by the equation 

2C«oHi80s6+8HO — 8(C 7 H0 3 .2HO) + CtaHaeOu 



Tannic acid. 



Gallic acid. 



Grape-sugar. 



418 VEGETABLE ACIDS. 

strikes a deep green colour with the salts of sesquioxide of iron. This body 
is said to be convertible by heat into tannic acid. 

The formula which has been assigned to catechin is Cj 5 IT 6 6 . 

Japonic and rubic acids are formed by the action of alkali in excess upon 
catechin ; the fii'st in the caustic condition, and the second when in the state 
of carbonate. Japonic acid is a black and nearly insoluble substance, so- 
luble in alkalis and precipitated by acids, containing C ]2 H 4 4 ,HO; it is per- 
haps identical with a black substance of acid properties, formed by M. 
Peligot, by heating grape-sugar with hydrate of baryta. Rubic acid has been 
but little studied ; it is said to form red insoluble compounds with the earths 
and certain oxides of the metals. 

Several acids closely allied to tannic acid have been found in coffee and 
Paraguay tea. 

Gallic acid. — Gallic acid is not nearly so abundant as tannic acid ; it is 
produced by an alteration of the latter. A solution of tannic acid in water 
exposed to the air, gradually absorbs oxygen, and deposits crystals of gallic 
acid, formed by the destruction of the tannic acid. The simplest method 
of preparing this acid in quantity is to take powdered nut-galls, which, 
when fresh and of good quality, contain 30 or 40 per cent, of tannic acid, 
with scarcely more than a trace of gallic, to mix this powder with water to 
a thin paste, and to expose the mixture to the air in a warm situation for 
the space of two or three months, adding water from time to time to replace 
that lost by drying up. The mouldy, dark-coloured mass produced may 
then be strongly pressed in a cloth, and the solid portion boiled in a con- 
siderable quantity of water. The filtered solution deposits on cooling abun- 
dance of gallic acid, which may be drained and pressed, and finally purified 
by re-crystallization. It forms small, feathery, and nearly colourless crys- 
tals, which have a beautiful silky lustre ; it requires for solution 100 parts 
of cold, and only 3 parts of boiling water ; the solution has an acid and as- 
tringent taste, and is gradually decomposed by keeping. Gallic acid does 
not precipitate gelatin ; with salts of protoxide of iron no change is pro- 
duced, but with those of the sesquioxide a deep bluish-black precipitate 
falls, which disappears when the liquid is heated, from the reduction of the 
sesquioxide to the protoxide at the expense of the gallic acid. 

The salts of gallic acid present but little interest; those of the alkalis are 
soluble, and readily destroyed by oxidation in presence of excess of base, 
the solution acquiring after some time a nearly black colour ; the gallates 
of most of the other metallic oxides are insoluble. 

Gallic acid, dried at 212° (100°C), contains C 7 H0 3 ,2HO; the crystals con- 
tain an additional equivalent of water. 

The insoluble residue of woody fibre and other matters from which the 
gallic acid has been withdrawn by boiling water, contains a small quantity 
of another acid substance, which may be extracted by an alkali, and after- 
wards precipitated by an addition of hydrochloric acid, as a greyish inso- 
luble powder. It contains C 7 H 2 4 , when dried at 248° (120°C), or gallic 
acid minus 1 eq. of water. The term ellagic acid is given to this substance. 
M. Pelouze once observed its conversion into ordinary gallic acid. 

The conversion of tannic into gallic acid by oxidation is accompanied by 
a disengagement of carbonic acid, the volume of which equals that of the 
oxygen absorbed: the oxidizing action must therefore be confined to the car- 
bon, and may perhaps be thus represented : — 



1 eq. tannic acid C ls H g 12 1 (2 eq. gallic acid .... C 14 H 6 O 10 

V = -1 2 eq. water H 2 2 

8 eq. oxygen O g J ( 4 eq. carbonic acid C 4 8 



C 18^8^20 



VEGETABLE ACIDS. 41& 

Much of the gallic acid is subsequently destroyed, in all probability onlv 
a part of that first produced escaping. 

The changes which gallic acid suffers when exposed to heat are very in- 
teresting. Heated in a retort by means of an oil-bath, the temperature of 
which is steadily maintained at 420° (215°C), or thereabouts, it is resolved 
into carbonic acid, and a new acid which sublimes into the neck of the re- 
tort in brilliant, crystalline plates, of the most perfect whiteness ; an insig- 
nificant residue of black matter remains behind. The term pyrogallic acid 
is given to the volatile product. It dissolves with facility in water, but the 
solution cannot be evaporated without blackening and decomposition ; it 
communicates a blackish-blue colour to salts of the protoxide of iron, and 
reduces those of the sesquioxide to the state of protoxide. An alkaline so- 
lution of this acid absorbs a very considerable quantity of oxygen, and has 
lately been employed with great advantage by Professor Liebig for the pur- 
pose of determining the amount of oxygen in atmospheric air. (See page 
121.) The acid characters of this substance are very indistinct. Pyiogallio 
acid contains C 6 H 3 3 . 

When dry gallic acid is suddenly heated to 480° (249°C), or above, it is 
decomposed into carbonic acid, water, and a second new acid, the metagallic, 
which remains in the retort as a black, shining mass, resembling charcoal ; 
a few crystals of pyrogallic acid are formed at the same time. Metagallic 
acid is insoluble in water, but dissolves in alkalis, and is again precipitated 
as a black powder by the addition of an acid. It combines with the oxides 
of lead and silver, and is composed of C 6 H 2 2 . Pyrogallic acid, also, exposed 
to the requisite temperature, yields metagallic acid, with separation of water. 

Tannic acid, under similar circumstances, furnishes the same products as 
gallic acid. Dr. Stenhouse has shown that pyrogallic acid may be procured 
in considerable quantity by carefully heating the dried aqueous extract of 
gall-nuts in Dr. Moh's subliming apparatus, already described. All these 
changes admit of simple explanation. 

= C 6 H 3 3 -f C0 2 

Dry gallic acid. Pyrogallic acid. 




= C 6 H 2 2 + HO 

Pyrogallic acid. Metagallic acid. 

3(C 18 H 5 9 ,3HO) = 6(C 7 H0 3 ,2HO) + 2C 6 H 3 3 



Tannic acid. Gallic acid. Pyrogallic acid. 

These phenomena present admirable illustrations of the production of 
pyrogen-acids by the agency of heat. 



420 CYANOGEN 



SECTION IV. 

AZOTIZED ORGANIC PRINCIPLES OF SIMPLE CONSTITUTION. 



CYANOGEN, ITS COMPOUNDS AND DERIVATIVES. 

Cyanogen 1 forms the most perfect type of a quasi-simple sub-radical that 
chemistry presents, as kakodyl does of the basyle class ; it is interesting 
also from being the first-discovered body of the kind. 

Cyanogen may be prepared with the utmost ease by heating in a small 
retort of hard glass the salt called cyanide of mercury, previously reduced to 
powder, and well dried. The cyanide undergoes decomposition, like the 
oxide under similar circumstances, yielding metallic mercury, a small quan- 
tity of a brown substance of which mention will again be made, and cyanogen 
itself, a colourless, permanent gas, which must be collected over mercury. 
It has a pungent and very peculiar odour, remotely resembling that of peach- 
kernels, or hydrocyanic acid ; exposed while at the temperature of 45° 
(7°-2C) to a pressure of 3-6 atmospheres, it condenses to a thin, colourless, 
transparent liquid. Cyanogen is inflammable ; it burns with a beautiful pur- 
ple, or peach-blossom coloured flame, generating carbonic acid and liberating 
nitrogen. The specific gravity of this gas is 1*806 ; it is composed of carbon 
and nitrogen in the proportion of 2 equivalents of the former to 1 equivalent 
of the latter, or C 2 N ; this is easily proved by mixing it with twice its mea- 
sure of pure oxygen, and firing the mixture in the eudiometer ; carbonic acid 
is formed equal in volume to the oxygen employed, and a volume of nitrogen 
equal to that of the cyanogen is set free. Cyanogen, in its capacity of quasi- 
element, is designated by the symbol Cy. Water dissolves 4 or 5 times its 
volume of cyanogen-gas, and alcohol a much larger quantity : the solution 
rapidly decomposes, yielding oxalate of ammonia, C 2 N-f-4HO = NH 4 0,C 2 3 , 
brown insoluble matter, and other products. 

Paracyanogen. — This is the brown or blackish substance above referred 
to, which is always formed in small quantity when cyanogen is prepared by 
heating the cyanide of mercury, and probably also, by the decomposition of 
solutions of cyanogen and of hydrocyanic acid. It is insoluble in water and 
alcohol, is dissipated by a very high temperature, and contains, according to 
Professor Johnson, carbon and nitrogen in the same proportions as in cya- 
nogen. , 

Cyanide or hydrogen ; hydrocyanic or prussic acid, HCy. — This very 
important compound, so remarkable for its poisonous properties, was disco- 
vered as early as 1782, by Scheele. It may be prepared in a state of purity, 
and anhydrous, by the following process : A long glass tube filled with dry 
cyanide of mercury, is connected by one extremity with an arrangement for 
furnishing dry sulphuretted-hydrogen gas, while a narrow tube attached to 
the other end is made to pass into a narrow-necked phial plunged into a 
freezing-mixture. Gentle heat is applied to the tube, the contents of which 

1 So called from kvuvos, blue, and ycvvdu), I generate. 



CYANOGEN. 



421 



suffer decomposition in contact "with the gas, sulphide of mercury and cya- 
nide of hydrogen being produced ; the latter is condensed in the receiver to 
the liquid form. A little of the cyanide of mercury should be left undecom- 
posed, to avoid contamination of the product by sulphuretted hydrogen. 
The pure acid is a thin, colourless, and exceedingly volatile liquid, which 
has a density of 0-7058 at 45° (7°-6C), boils at 79° (26°-lC), and solidifies, 
■when cooled to 0° ( — 17°-8C) ; its odour is very powerful and most charac- 
teristic, much resembling that of peach-blossoms or bitter-almond oil ; it 
has a very feeble acid reaction, and mixes with water and alcohol in all pro- 
portions. In the anhydrous state this substance constitutes one of the most 
formidable poisons known, and even when largely diluted with water, its 
effects upon the animal system are exceedingly energetic ; it is employed, 
however, in medicine in very small doses. The inhalation of the vapour 
should be carefully avoided in all experiments in which hydrocyanic acid is 
concerned, as it produces headache, giddiness, and other disagreeable symp- 
toms : ammonia and chlorine are the best antidotes. 

The acid in its pure form can seldom be preserved; even when enclosed 
in a carefully-stopped bottle it is observed after a very short time to darken, 
and eventually to deposit a black substance containing carbon, nitrogen, and 
perhaps hydrogen ; ammonia is formed at the same time, and many other 
products. Light favours this decomposition. Even in a dilute condition it 
is apt to decompose, becoming brown and turbid, but not always with the 
same facility, some samples resisting change for a great length of time, and 
then suddenly solidifying to a brown, pasty mass in a few weeks. 

"When hydrocyanic acid is mixed with concentrated mineral acids, the 
hydrochloric for example, the whole solidifies to a crystalline paste of sal- 
ammoniac and hydrated formic acid ; a reaction which is explained in a very 
simple manner, 1 eq. of hydrocyanic acid and 4 eq. water, yielding 1 eq. of 
ammonia and 1 eq. of formic acid. 

C 2 N,H + 4HO = NE 3 -f C 2 H0 3 ,H<X 

On the other hand, when dry formate of ammonia is heated to 392° 
(200°C), it is almost entirely converted into hydrocyanic acid and water. 
NH 4 0,C 3 HOa = C 2 N,H -f 4HO. 

Aqueous solution of hydrocyanic acid may be made by various means. 
The most economical, and by far the best, where considerable quantities are 
wanted, is to decompose at a boiling-heat the ^yellow ferrocyanide of potas- 
sium by diluted sulphuric acid. For example, 500 grains of the powdered 
ferrocyanide may be dissolved in four or five ounces of warm water, and 
introduced into a capacious flask or globe capable of being connected by a 
perforated cork and wide bent tube with a Liebig's condenser well supplied 
with cold water ; 300 grains of oil of vitriol are diluted with three or four 
times as much water and added to the contents of the flask ; distillation is 
carried on until about one-half of the liquid has distilled over, after which 
the process may be interrupted. The theory of this process has been care- 
fully studied by Mr. Everitt ; * it is sufficiently complicated. 



2 eq. ferrocy- 
anide of po- 
tassium 



3 eq. water 



6 eq. sulphuric acid 



6 eq. carbon 
6 eq. carbon 
3 eq. nitrogen 
3 eq. nitrogen 

1 eq. potassium 
3 eq. potassium 

2 eq. iron 
j 3 eq. hydrogen 
\ 3 eq. oxygen 




Insoluble yellow salt. 



eq. hydrocyanic acid. 

3 eq. bisulphate of po- 
tassa. 



1 l'hil. Magazine. Feb. 1S35. 



422 CYANOGEN, 

The substance described in the preceding diagram as insoluble yellow salt re- 
mains in the flask after the reaction, together with the bisulphate of potassa ; 
it contains the elements of 2 eq. cyanide of iron, and 1 eq. cyanide potas- 
sium, but its constitution is unknown. On exposure to the air, it rapidly 
becomes blue. 

When hydrocyanic acid is wanted for purposes of pharmacy, it is best to 
prepare a strong solution in the manner above described, and then, having 
ascertained its exact strength, to dilute it with pure water to the standard 
of the Pharmacopoeia, viz., 2 per cent, of real acid. This examination is 
best made by precipitating with excess of nitrate of silver a known weight 
of the acid to be tried, collecting the insoluble cyanide of silver upon a small 
filter previously weighed, washing, drying, and lastly re-weighing the whole. 
From the weight of the cyanide that of the hydrocyanic acid can be easily 
calculated, an equivalent of the one corresponding to an equivalent of the 
other ; or the weight of the cyanide of silver may be divided by 5, which 
will give a close approximation to the truth. 

Another very elegant method for determining the amount of hydrocyanic 
acid in a liquid has been lately suggested by Prof. Liebig. It is based upon 
the property possessed by cyanide of potassium of dissolving a quantity of 
chloride of silver sufficient to produce with it a double cyanide containing 
equal equivalents of cyanide of silver and of potassium (KCy,AgyCy). Hence 
a solution of hydrocyanic acid, which is super-saturated with potassa, and 
mixed with a few drops of solution of common salt, will not yield a perma- 
nent precipitate with nitrate of silver before the whole of the hydrocyanic 
acid is converted into the above double salt. If we know the amount of 
silver in a given volume of the nitrate-solution, it is easy to calculate the 
quantity of hydrocyanic acid, for this quantity will stand to the amount of 
silver in the nitrate consumed, as 2 eq. of hydrocyanic acid to 1 eq. of 
silver, i. e. 

108 : 54 = silver consumed : x. 

It is a common remark, that •ih^hydrocyanic acid made from ferrocyanide 
of potassium keeps better th«*n/that made by other means. The cause of 
this is ascribed to the presence 'of a trace of mineral acid. Mi*. Everitt ac 
tually found that a few drops of hydrochloric acid, added to a large bulk of 
the pure dilute acid, preserved it from decomposition, while another portion, 
not so treated, became completely spoiled. 

A very convenient process for the extemporaneous preparation of an acid 
of definite strength, is to decompose a known quantity of cyanide of potas- 
sium by solution of tartaric 'acid: 100 grains of crystallized tartaric acid in 
powder, 44 grains of cyanide of potassium, and 2 measured ounces of distilled 
water, shaken up in a phial for a few seconds, and then left at rest, in order 
that the precipitate may subside, will yield an acid of very nearly the required 
strength. A little alcohol may be added to complete the separation of the 
cream of tartar ; no filtration or other treatment need be employed. 

The production of hydrocyanic acid from bitter-almonds has been already 
mentioned in connection with the history of the volatile oil. Bitter-almonds, 
the kernels of plums and peaches, the seeds of the apple, the leaves of the 
cherry-laurel, and various other parts of plants belonging to the great natural 
order, rosacece, yield on distillation with water, a sweet-smelling liquid, con- 
taining hydrocyanic acid. This is probably due in all cases to the decompo- 
sition of the amygdalin, pre-existent in the organic structure. The change 
in question is brought about, in a very singular manner, by the presence of 
a soluble azotized substance, called emulsin or synajHase, which forms a large 
proportion of the white pulp of both bitter and sweet almonds. This sub- 
stance bears a somewhat similar relation to amygdalin, that diastase, which 



ITS COMPOUNDS AND DERIVATIVES. 423 

it closely resembles in many particulars, does to starch. Hydrocyanic acid 
exists ready-formed to a considerable extent in the juice of the bitter cassava. 

Amtgdalix is prepared "with facility by the following process : — The paste 
of bitter-almonds, from -which the fixed oil has been expressed, is exhausted 
with boiling alcohol: this coagulates and renders inactive the synaptase, 
while at the same time it dissolves out the amygdalin. The alcoholic liquid 
is distilled in a water-bath, by which much of the spirit is recovered, and 
the syrupy residue diluted with water, mixed with a little yeast, and set in 
a warm place to ferment ; a portion of sugar, present in the almonds, is thus 
destroyed. The filtered liquid is then evaporated to a syrupy state in a 
water-bath, and mixed with a quantity of alcohol, which throws down the 
amygdalin as a white crystalline powder ; the latter is collected on a cloth 
filter, pressed, re-dissolved in boiling alcohol, and left to cool. It separates 
in small crystalline plates, of pearly ■whiteness, which are inodorous and 
nearly tasteless ; it is decomposed by heat, leaving a bulky coal, and diffusing 
the odour of the hawthorn. In water, both hot and cold, amygdalin is very 
insoluble : a hot saturated solution deposits, on cooling, brilliant prismatic 
crystals, which contain water. In cold alcohol it dissolves with great diffi- 
culty. Heated with dilute nitric acid, or a mixture of dilute sulphuric acid 
and binoxide of manganese, it is resolved into ammonia, bitter-almond oil, 
benzoic acid, formic acid, and carbonic acid; with permanganate of potassa, 
it yields a mixture of cyanate and benzoate of that base. 

Amygdalin is composed of C^H^NCW 

Synaptase itself has never been obtained in a state of purity, or fit for 
analysis : it is described as a yellowish-white, opaque, brittle mass, very 
soluble in water, and coagulable, like albumin, by heat, in which case it 
loses its specific property. In solution it very soon becomes turbid and pu- 
trefies. The decomposition of amygdalin under the influence of this body 
may be elegantly studied by dissolving a portion in a large quantity of water, 
and adding a little emulsion of sweet-almond ; the odour of the volatile oil 
immediately becomes apparent, and the liquor yields, on distillation, hydro- 
cyanic acid. The nature of the decomposition may be thus approximately 
represented : — 

f 1 eq. hydrocyanic acid C 2 H X 
, , ,. '' 2 eq. bitter-almond oil G-H, 0, 

rVvvf ' \ ™&* C> U 

<-40 u 27- NU 22 ' o ^ forlg g c acid c 4 2 2 0q 

5 eq. wate* ,. A H - 0= 

■ » / 

It may be observed that in preparing bitfer-almond oil the paste should 
be well mixed with about 20 parts of warm water, and the whole left to 
stand some hours before distillation : the heat must be gently raised to avoid 
coagulating the synaptase before it has had ti$ie to act upon the amygdalin. 
Almond-paste, thrown into boiling water, yields little or no bitter-almond oil. 

A>rrGDALic acid. — When amygdalin is boiled with an alkali or an 
alkaline earth, it is decomposed into ammonia, and a new acid called the 
amygdalic, which remains in union with the base. This is best prepared by 
means of baryta-water, the ebullition being continued as long as ammonia, 
is evolved. From the solution thus obtained, the baryta may be precipi- 
tated by dilute sulphuric acid : the filtered liquid is evaporated in a water- 
bath. Amygdalic acid forms a colourless, transparent, amorphous mass, 
very soluble in water, and deliquescent in moist air : the solution has an 
acid taste and reaction. It is converted by oxidizing agents into fitter- 



424 CYANOGEN : 



almond oil, formic, and benzoic acids. The amygdalates are mostly soluble, 
but have been but little studied ; the acid contains C 40 H 26 O 24 ,HO. 

The presence of hydrocyanic acid is detected with the utmost ease ; its 
remai'kable odour and high degree of volatility almost sufficiently charac- 
terize it. With solution of nitrate of silver it gives a dense curdy white pre- 
cipitate, much resembling the chloride, but differing from that substance in 
not blackening so readily by light, in being soluble in boiling nitric acid, 
and in suffering complete decomposition when heated in a dry state, metallic 
silver being left ; the chloride, under the same circumstances, merely fuses, 
but undergoes no chemical change. Tha production of Prussian blue by 
" Scheele's test" is an excellent and most decisive experiment, which may 
be made with a very small quantity of acid. The liquid to be examined is 
mixed with a few drops of solution of sulphate of protoxide of iron and an 
excess of caustic potassa, and the whole exposed to the air for 10 or 15 
minutes, with agitation ; hydrochloric acid is then added in excess, which 
dissolves the oxide of iron, and, if hydrocyanic acid be present, leaves 
Prussian blue as an insoluble powder. The reaction becomes quite intel- 
ligible when the production of a ferrocyanide, described a few pages hence, 
is understood. See page 432. 

Another elegant process for detecting hydrocyanic acid is mentioned in the 
article upon hydrosulphocyanic acid. 

The most important of the metallic cyanides are the following ; they bear 
the most perfect analogy to the haloid-salts. 

Cyanide of Potassium, KCy. — When potassium is heated in cyanogen 
gas, it takes fire and burns in a \ery beautiful manner, yielding cyanide of 
the metal ; the same substance is produced when potassium is heated in the 
vapour of hydrocyanic acid, hydrogen being liberated. If pure nitrogen 
gas be transmitted through a white-hot tube, containing a mixture of car- 
bonate of potassa and charcoal, a considerable quantity of cyanide of potas- 
sium is formed, which settles in the cooler portions of the tube as a white 
amorphous powder; carbonic oxide is at the same time extricated. If 
azotized organic matter of any kind, capable of furnishing ammonia by 
destructive distillation, as horn-shavings, parings of hides, &c, be heated 
to redness with carbonate of potassa in a close vessel, a very abundant pro- 
duction of cyanide of potassium results, which cannot however be advan- 
tageously extracted by direct means, but in practice is always converted 
into ferrocyanide, which is a much more stable substance, and crystallizes 
better. 

There are several methods by which cyanide of potassium may be pre- 
pared for use. It may be made by passing the vapour of hydrocyanic acid 
into a cold alcoholic solution of potassa ; the salt is deposited in a crystal- 
line form, and may be separated from the liquid, pressed and dried. Ferro- 
cyanide of potassium, heated to whiteness in a nearly close vessel, evolves 
nitrogen and other gases, and leaves a mixture of charcoal, carbide of iron, 
and cyanide of potassium, which latter salt is not decomposed unless the 
temperature be excessively high. Mr. Donovan recommends the use in this 
process of a wrought-iron mercury-bottle, which is to be half filled with the 
ferrocyanide, and arranged in a good air-furnace, capable of giving the 
requisite degree of heat ; a bent iron tube is fitted to the mouth of the 
bottle and made to dip half an inch into a vessel of water ; this serves to 
give exit to the gas. The bottle is gently heated at first, but the tempera- 
ture ultimately raised to whiteness ; when no more gas issues, the tube is 
stopped with a cork, and, when the whole is completely cold, the bottle is 
cut asunder in the middle by means of a chisel and sledge-hammer, and the 
pure white fused salt carefully separated from the black spongy mass below, 
and preserved in a well-stopped bottle ; the black substance contains much 



ITS COMPOUNDS AND DERIVATIVES. 425 

cyanide, which may be extracted by a little cold water. It would be better, 
perhaps, in the foregoing process, to deprive the ferrocyanide of potassium 
of its water of crystallization before introducing it into the iron vessel. 

Professor Liebig has published a very easy and excellent process for 
making cyanide of potassium, which does not, however, yield it pure, but 
mixed with cyanate of potassa. For most of the applications of cyanide 
of potassium, as, for example, electro-plating and gilding, for which a con- 
siderable quantity is now required, this impurity is of no consequence. 8 
parts of ferrocj^anide of potassium are rendered anhydrous by gentle heat, 
and intimately mixed with 3 parts of dry carbonate of potassa ; this mix- 
ture is thrown into a red-hot earthen crucible, and kept in fusion, with occa- 
sional stirring, until gas ceases to be evolved, and the fluid portion of the 
mass becomes colourless. The crucible is left at rest for a moment, and 
then the clear salt decanted from the heavy black sediment at the bottom, 
which is principally metallic iron in a state of minute division. In this 
experiment, 2 eq. of ferrocyanide of potassium and 2 eq. carbonate of 
potassa yield 5 eq. cyanide of potassium, 1 eq. cyanate of potassa, 2 eq. 
iron, and 2 eq. carbonic acid. The product may be advantageously used, 
instead of ferrocyanide of potassium, in the preparation of hydrated hydro- 
cyanic acid, by distillation with diluted oil of vitriol. 

Cyanide of potassium forms colourless, cubic or octahedral crystals, deli- 
quescent in the air, and exceedingly soluble in water ; it dissolves in boiling 
alcohol, but separates in great measure on cooling. It is readily fusible, and 
undergoes no change at a moderate red, or even white-heat, when excluded 
from air ; otherwise, oxygen is absorbed and the cyanide of potassium 
becomes cyanate of potassa. Its solution always has an alkaline reaction, 
and exhales when exposed to the air the smell of hydrocyanic acid ; it is 
decomposed by the feeblest acids, even the carbonic acid of the atmosphere, 
and when boiled in a retort is slowly converted into formate of potassa with 
separation of ammonia. This salt is anhydrous ; it is said to be as poisonous 
as hydrocyanic acid itself. 

Cyanide of potassium has been derived from a curious and unexpected 
source. In some of the iron-furnaces in Scotland where raw-coal is used 
for fuel with the hot blast, a saline-looking substance is occasionally observed 
to issue in a fused state from the tuyere-holes of the furnace, and concrete 
on the outside. This proved, on examination by Dr. Clark, to be principally 
cyanide of potassium. 

Cyanide of sodium, NaCy, is a very soluble salt, corresponding closely 
with the foregoing, and obtained by similar means. 

Cyanide of ammonium, NH 4 Cy. — This is a colourless, crystallizable, and 
very volatile substance, prepared by distilling a mixture of cyanide of potas- 
sium and sal-ammoniac, or by mingling the vapour of anhydrous hydrocyanic 
acid with ammoniacal gas, ^or, lastly, according to the observation of M. 
Langlois, by passing ammonia over red-hot charcoal. It is very soluble in 
water, subject to spontaneous decomposition, and is highly poisonous. 

Cyanide of mercury, HgCy. — One of the most remarkable features in 
the history of cyanogen is its powerful attraction for certain of the less 
oxidable metals, as silver, and more particularly mercury and palladium. 
Dilute hydrocyanic acid dissolves finely-powdered red oxide of mercury with 
the utmost ease ; the liquid loses all odour, and yields on evaporation crys- 
tals of cyanide of mercury. Cyanide of potassium is in like manner decom- 
posed by red oxide of mercury, hydrate of potassa being produced. Cyanide 
of mercury is generally prepared from common ferrocyanide of potassium ; 
2 parts of the salt are dissolved in 15 parts of hot water, and 3 parts of dry 
sulphate of mercury added ; the whole is boiled for 15 minutes, and filtered 
hot from the oxide of iron, which separates. The solution, on cooling 
3G* 



120 CYANOGEN, 

deposits the new salt in crystals. Cyanide of mercury forms white, trans- 
lucent prisms, much resembling those of corrosive sublimate; it is soluble 
in 8 parts of cold water, and in a much smaller quantity at a higher tempe- 
rature, and also in alcohol. The solution has a disagreeable, metallic taste, 
is very poisonous, and is not precipitated by alkalis. Cyanide of mercury is 
u,sed in the laboratory as a source of cyanogen. 

Cyanide of silver, AgCy, has been already described. Cyanide of zinc, 
ZnCy, is a white insoluble powder, prepared by mixing acetate of zinc with 
hydrocyanic acid. Cyanide of cobalt, CoCy, is obtained by similar means : 
it is dirty white, and insoluble. Cyanide of palladium forms a pale, whitish 
precipitate when the chloride of that metal is mixed with a soluble cyanide, 
including that of mercury. Tercyanide of gold, AuCy 8 , is yellowish-white 
and insoluble, but freely dissolved by solution of cyanide of potassium. 
Protocyanide of iron has not been obtained, from the tendency of the metal 
to pass into the radical, and generate a ferrocyanide. An insoluble green 
compound containing FeCy,F 2 Cy 8 was formed by M. Pelouze by passing chic 
rine gas into a boiling solution of ferrocyanide of potassium. 

Cyanic and cyanuric acids. — These are two remarkable isomeric bodies, 
related in a very close and intimate manner, and presenting phenomena of 
great interest. Cyanic acid is the true oxide of cyanogen ; it is formed in 
conjunction with cyanide of potassium, when cyanogen gas is transmitted 
over heated hydrate or carbonate of potassa, or passed into a solution of 
the alkaline base, the reaction resembling that by which chlorate of potassa 
and chloride of potassium are generated when the oxide and the salt-radical 
are presented to each other. Cyanate of potassa is, more%er, formed when 
the cyanide is exposed to a high temperature with access of air ; unlike the 
chlorate, it bears a full red-heat without decomposition. 

Hydrated Cyanic Acid, CyO,HO, is procured by heating to dull redness in 
a hard glass retort connected with a receiver cooled by ice, cyanuric acid, 
deprived of its water of crystallization. The cyanuric acid is resolved, with- 
out any other product, into hydrated cyanic acid, which condenses in the 
receiver to a limpid, colourless liquid, of exceedingly pungent and penetra- 
ting odour, like that of the strongest acetic acid ; it even blisters the skin. 
When mixed with water, it decomposes almost immediately, giving rise to 
bicarbonate of ammonia. 

C 2 NO,HO+2HO=C 2 4 -fNH 3 . 

This is the reason why the hydrated acid cannot be separated from a 
cyanate by a stronger acid. A trace of cyanic acid, however, always escapes 
decomposition, and communicates to the carbonic acid evolved a pungent 
smell similar to that of the sulphurous acid. The cyanates may be easily 
distinguished by this smell, and by the simultaneous formation of an ammo- 
nia-salt, which remains behind. 

The pure hydrated cyanic acid cannot be preserved ; shortly after its pre- 
paration it changes spontaneously, with sudden elevation of temperature, 
into a solid, white, opaque, amorphous substance, called cyamelide. This 
curious body has the same composition as hydrated cyanic acid; it is inso- 
luble in water, alcohol, ether, and dilute acids ; it dissolves in strong oil cf 
vitriol by the aid of heat, with evolution of carbonic acid and production 
of ammonia ; boiled with solution of caustic alkali, it dissolves, ammonia ia 
disengaged, and a mixture of cyanate and cyanurate of the base generated. 
By dry distillation it is again converted into the hydrate of cyanic acid. 

Cyanate of potassa, KOjCyO. — The best method of preparing this salt, 
is, according to Liebig, to oxidize cyanide of potassium by means of litharge. 
The cyanide, already containing a portion of cyanate, described p. 425, is 
re-melted in an earthen crucible, and finely powdered protoxide of lead added 



ITS COMPOUNDS AND DERIVATIVES. 427 

by small portions ; the oxide is instantaneously reduced, and the metal, at 
first in a state of minute division, ultimately collects to a fused globule at the 
bottom of the crucible. The salt is poured out, and, when cold, powdered 
and boiled with alcohol ; the hot filtered solution deposits crystals of cyanate 
of potassa on cooling. The great de-oxidizing power exerted by cyanide of 
potassium at a high temperature promises to render it a valuable agent in 
many of the finer metallurgic operations. 

Another method of preparing the cyanide is to mix dried and finely-pow- 
dered fexrocyanide of potassium with half its weight of equally dry binoxide 
of manganese ; to heat this mixture in a shallow iron ladle with free expo- 
sure to air and frequent stirring until the tinder-like combustion is at an end, 
and to boil the residue in alcohol, which extracts the cyanate of potassa. 

This salt crystallizes from alcohol in thin, colourless, transparent plates, 
which suffer no change in dry air, but on exposure to moisture become gra- 
dually converted, without much alteration of appearance, into bicarbonate 
of potassa, ammonia being at the same time disengaged. Water dissolves the 
cyanate of potassa in large quantity ; the solution is slowly decomposed in 
the cold, and rapidly at a boiling heat, into bicarbonate of potassa and am- 
monia. When a concentrated solution is mixed with a small quantity of 
dilute mineral acid, a precipitate falls, which consists of acid cyanurate of 
potassa. Cyanate of potassa is reduced to cyanide of potassium by ignition 
with charcoal in a covered crucible. 

Cyanate of potassa, mixed with solutions of lead and silver, gives rise to 
insoluble cyanates of the oxides of those metals, which are white. 

Cyanate of ammonia ; urea. — When the vapour of hydrated cyanic acid 
is mixed with excess of ammoniacal gas, a white, crystalline, solid substance 
is produced, which has all the characters of a true, although not neutral, 
cyanate of ammonia. It dissolves in water, and, if mixed with an acid, evolves 
carbonic acid gas ; with an alkali, it yields ammonia. If the solution be 
heated, or if the crystals be merely exposed a certain time to the air, a por- 
tion of ammonia is dissipated, and the properties of the compound completely 
changed. It may now be mixed with acids without the least symptoms of 
decomposition, while cold caustic alkali, on the other hand, fails to discharge 
the smallest trace of ammonia. The result of this curious metamorphosis of 
the cyanate is a substance called urea, a product of the animal body, the 
chief and characteristic constituent of urine. This artificial formation of one 
of the products of organic life cannot fail to possess great interest. Its dis- 
covery is due to Prof. Wohler. The properties of urea, and the most advan- 
tageous methods of preparing it, will be found described a few pages hence. 

Cyanuric acid. — The substance called melam, of which farther mention 
will be made, is dissolved by gentle heat in concentrated sulphuric acid, the 
solution mixed with 20 or 30 parts of water, and the whole maintained at a 
temperature approaching the boiling-point, until the specimen of the liquid, 
on being tried by ammonia, no longer gives a white precipitate : several days 
are required. The liquid, concentrated by evaporation, deposits on cooling 
cyanuric acid, which is purified by re-crystallization. Another, and perhaps 
simpler method, is to heat dry and pure urea in a flask or retort: the sub- 
stance melts, boils, disengages ammonia in large quantity, and at length 
becomes converted into a dirty white, solid, amorphous mass, which is impure 
cyanuric acid. This is dissolved by the aid of heat in strong oil of vitriol, 
and nitric acid added by little and little until the liquid becomes nearly 
colourless ; it is then mixed with water, and suffered to cool, whereupon the 
cyanuric acid separates. The urea may likewise be decomposed very con- 
veniently by gently heating it in a tube, while dry chlorine gas passes over 
it. A mixture of cyanuric acid and sal-ammoniac results, which is separated 
by dissolving in water. 



428 CYANOGEN, 

Cyanuric acid in a pure state forms colourless crystals, seldom of large 
size, derived from an oblique rhombic prism, -which effloresce in a dry atmo- 
sphere from loss of water. It is very soluble in cold water, and requires 24 
parts for solution at a boiling heat; it reddens litmus feebly, has no odour, 
and but little taste. This acid is tribasic; the crystals contain C 6 N 3 3 ,3HO 
-J-4HO, and are easily deprived of the 4 eq. of water of crystallization. In 
point of stability, it oifers a most remarkable contrast to its isomer, cyanic 
acid ; it dissolves, as above indicated, in hot oil of vitriol, and even in strong 
nitric acid, without decomposition, and in fact crystallizes from the latter in 
an anhydrous state, containing C 6 N 3 3 ,3HO. Long-continued boiling with 
these powerful agents resolves it into ammonia and carbonic acid. 

The connection between cyanic acid, urea, and cyanuric acid may be thus 
recapitulated : — 

Cyanate of ammonia is converted by heat into urea. 
Urea is decomposed by the same means into cyanuric acid and urea. 
Cyanuric acid is changed by a very high temperature into hydrated cyanic 
acid. 

In the latter reaction, 1 eq. of hydrated cyanuric acid splits into 3 eq. hy- 
drated cyanic acid. 

C 6 N 3 3 ,3HO=3(C 2 NO,HO). 

Cyanate and cyanurate of oxide or ethyl. — If a dry mixture of cya- 
nate of potassa and sulphovinate of potassa be distilled, a product is ob- 
tained which consists of a mixture of the above ethers. They are separated 
without difficulty, the cyanate boiling at 140° (60°C), while the boiling point 
of the cyanurate is much higher, namely, 528° -8 (276°C). Cyanate of ethyl 
is a mobile liquid, the vapour of which excites a flow of tears. The com- 
position of cyanate of ethyl is C 6 H 5 N0 2 ==C 4 H 5 0,C 2 NO==AeO,CyO. The 
formation is represented by the equation KO,CyO-f-KO,AeO,2S0 3 =AeO, 
CyO-f-2(KO,S0 3 ). The cyanurate of ethyl contains 3AeO,C 6 N 3 3 ; it arises 
in this reaction from the coalescence of 3 eq. of cyanate of ethyl. It may 
be likewise obtained by distilling a mixture of sulphovinate of potassa with 
cyanurate of potassa. Cyanurate of ethyl is a crystalline mass, slightly so- 
luble in water, readily soluble in alcohol and ether, fusing at 185° (85°C). 
By substituting for sulphovinate of potassa, salts of sulphomethylic and sul- 
phamylic acid, the corresponding methyl- and amyl-compounds may be ob- 
tained. 

The study of the cyanic and cyanuric ethers, which were discovered by 
Wurtz, has led to very important results, which will be fully described in the 
section on the organic bases. 

Fulminic acid. — This remarkable compound, which is isomeric both with 
cyanic and cyanuric acids, originates in the peculiar action exercised by ni- 
trous acid upon alcohol in presence of a salt of silver or mercury. Neither 
absolute fulminic acid nor its hydrate has ever been obtained. 

Fulminate of silver is prepared by dissolving 40 or 50 grains of silver, 
which need not be pure, in f oz. by measure of nitric acid of sp. gr. 1-37 or 
thereabouts, by the aid of a little heat ; a sixpence answers the purpose vei-y 
well. To the highly acid solution, while still hot, 2 measured ounces of al- 
cohol are added, and heat applied until reaction commences. The nitric acid 
oxidizes part of the alcohol to aldehyde and oxalic acid, becoming itself re- 
duced to nitrous acid, which in turn acts upon the alcohol in such a manner 
as to form nitrous ether, fulminic acid, and water. 1 eq. nitrous ether and 
1 eq. of nitious acid containing the elements of 1 eq. fulminic acid and 5 
eq. water. 

C 4 H 5 0, NO, -f N0 3 = C 4 N 2 2 -f 5TIO. 



ITS COMPOUNDS AND DERIVATIVES. 429 

The fulminate of silver slowly separates from the hot liquid in the form 
of small, brilliant, white, crystalline plates, which may be washed with a 
little cold water, distributed upon separate pieces of filter-paper in portions 
not exceeding a grain or two each, and left to dry in a warm place. When 
dry, the papers are folded up and preserved in a box or bottle. This is the 
only safe method of keeping the salt. Fulminate of silver is soluble in 86 
parts of boiling water, but the greater part crystallizes out on cooling ; it is 
one of the most dangerous substances to handle that chemistry presents ; it 
explodes when strongly heated, or when rubbed or struck with a hard body, 
or when touched with concentrated sulphuric acid, with a degree of violence 
almost indescribable ; the metal is reduced, and a large volume of gaseous 
matter suddenly liberated. Strange to say, it may, when very cautiously 
mixed with oxide of copper, be burned in a tube with as much facility as 
any other organic substance. Its composition thus determined is expressed 
in the formula 2AgO,C 4 N 2 2 . 

The acid is evidently bibasic ; when fulminate of silver is digested with 
caustic potassa, one-half of the oxide is precipitated, and a compound pro- 
duced containing AgO,KO,C 4 N 2 2 , which resembles the neutral silver-salt, 
and detonates by a blow. Corresponding compounds containing soda and 
oxide of ammonium exist ; but a pure fulminate of an alkaline metal has 
never been formed. If fulminate of silver be digested with water and cop- 
per, or zinc, the silver is entirely displaced, and a fulminate of the new metal 
produced. The zinc-salt mixed with baryta- water gives rise to a precipitate 
of oxide of zinc, while fulminate of zinc and baryta, ZnO,BaO,C 4 N 2 2 , re- 
mains in solution. Fulminate of mercury is prepared by a process very 
similar to that by which the silver-salt is obtained ; one part of mercury is 
dissolved in 12 parts of nitric acid, and the solution mixed with an equal 
quantity of alcohol ; gentle heat is applied, and if the reaction becomes too 
violent, it may be moderated by the addition from time to time of more 
spirit, much carbonic acid, nitrogen, and red vapours are disengaged, to- 
gether with a large quantity of nitrous ether and aldehyde ; these are some- 
times condensed and collected for sale, but are said to contain hydrocyanic 
acid. The fulminate of mercury separates from the hot liquid, and after 
cooling may be purified from an admixture of reduced metal by solution in 
boiling water and re-crystallization. It much resembles the silver-salt in 
appearance, properties, and degree of solubility, and contains 2Hg 2 0,C 4 N 2 2 . 
It explodes violently by friction or percussion, but, unlike the silver-corn, 
pound, merely burn3 with a sudden and almost noiseless flash when kindled 
in the open air. It is manufactured on a large scale for the purpose of 
charging percussion-caps ; sulphur and chlorate of potassa, or more fre- 
quently nitre, are added, and the powder, pressed into the cap, is secured 
by a drop of varnish. 

The relations of composition between the three isomeric acids are beauti- 
fully seen by comparing their silver-salts ; the first acid is monobasic, the 
second bibasic, and the third tribasic. 

Cyanate of silver AgO , C 2 N 0. 

Fulminate of silver 2AgO , C 4 N 2 2 . 

Cyanurate of silver 3AgO , C 6 N 3 3 . 

Until quite recently, beyond the accidental one of identity of composition, 
no relation existed between fulminic acid and its isomers. Mr. Gladstone 
has, however, shown that, when a solution of fulminate of copper is mixed 
with excess of ammonia, filtered, treated with sulphuretted hydrogen in 
excess, and again filtered from the insoluble sulphide of copper, the liquid 
obtained is a mixed solution of urea and-sulphocyanide of ammonium. 

Chlorides of cyanogen. — Chlorine forms two compounds with cyanogen 



430 FERROC YANOGEN AND ITS COMPOUNDS. 

or its elements, which are isomeric, and correspond to cyanic and cyanuric 
acids. Gaseous chloride of cyanogen, CyCl, is formed by conducting chlorine 
gas into strong hydrocyanic acid, or by passing chlorine over moist cyanide 
of mercury contained in a tube sheltered from the light. It is a permanent 
and colourless gas at the temperature of the air, of insupportable pungency, 
and soluble to a very considerable extent in water, alcohol, and ether. At 
0° ( — 17°-8C) it congeals to a mass of colourless crystals, ■which at 5° 
( — 15°C) melt to a liquid whose boiling-point is 11° ( — 11°-6C). At the tem- 
perature of the air it is condensed to the liquid form under a pressure of 
four atmospheres, and when long preserved in this condition in hermetically- 
sealed tubes it gradually passes into the solid modification. Solid chloride 
of cyanogen is generated when anhydrous hydrocyanic acid is put into a 
vessel of chlorine gas, and the whole exposed to the sun ; hydrochloric acid 
is formed at the same time. It forms long colourless needles, which exhale 
a powerful and offensive odour, compared by some to that of the excrement 
of mice ; it melts at 284° (140°C), and sublimes unchanged at a higher tem- 
perature. When heated in contact with water, it is decomposed into cyanuric 
and hydrochloric acids. This compound may be represented by the formula 
CygCl 3 , or C 6 N 3 ,C1 3 . It dissolves in alcohol and ether without decomposition. 
Bromide and iodide of cyanogen correspond to the first of the preceding 
compounds, and are prepared by distilling bromine or iodine with cyanide 
of mercury. They are colourless, volatile, solid substances, of powerful 
odour. 

FERROCYANOGEN AND ITS COMPOUNDS. 

When a solution of cyanide of potassium is digested with iron-filings at a 
gentle heat in an open vessel, oxygen is absorbed from the air, the iron dis- 
solves quietly and disappears, and a highly alkaline, yellow liquid is obtained, 
which on evaporation deposits lemon-yellow crystals containing potassium in 
combination with a new salt-radical composed of the metal iron and the ele- 
ments of cyanogen ; in the mother-liquid hydrate of potassa is found. 3 eq. 
cyanide of potassium, 1 eq. iron, and 1 eq. oxygen, yield 1 eq. of the new 
salt, and 1 eq. of potassa. 

3KCy-fFe-f = KO-f K 2 ,C 6 N 3 Fe. 

The new substance is called ferrocyUnogen, and is designated by the symbol 
Cfy ; it is bibasic, neutralizing 2 equivalents of metal or hydrogen, and con- 
tains the elements of 3 equivalents of cyanogen combined with 1 eq. of iron. 
It has never been isolated. 

When iron in filings is heated in a small retort with a solution of cyanide 
of potassium, it is dissolved with evolution of hydrogen, caustic potassa and 
the new substance being generated ; the oxygen in this case is derived from 
the decomposition of water. Sulphide of iron and cyanide of potassium give 
rise, under similar circumstances, to sulphide of potassium and ferrocyanide 
of potassium. 

Hydroferrocyanic acid, Cfy2H. — Ferrocyanide of lead or copper, both 
of which are insoluble, may be suspended in water, and decomposed by a 
stream of sulphuretted hydrogen gas. The filtered solution, evaporated in 
the vacuum of the air-pump over a surface of oil of vitriol, furnishes the acid 
in a solid form. If the aqueous solution be agitated with ether, nearly the 
whole of the acid separates in colourless, crystalline laminte ; it may even 
be made in large quantity by adding hydi-ochloric acid to a strong solution 
of ferrocyanide of potassium in water free from air, and shaking the whole 
with ether. The crystals may be dissolved in alcohol, and the acid again 
thrown d^wn by ether,, which possesses the remarkable property of precipi- 
tating this subi'tance from solution. ' Hydroferrocyanic acid differs completely 



FERROCYANOGEN AND ITS COMPOUNDS. 431 

from hydrocyanic acid ; its solution in water has a powerfully acid taste and 
reaction, and decomposes alkaline carbonates with effervescence ; it refuses 
to dissolve oxide of mercury in the cold, but when heat is applied, undergoes 
decomposition, forming cyanide of mercury and a peculiar compound of iron, 
cyanogen, and oxygen, with reduction of some of the oxide. In a dry state 
the acid is very permanent, but when long exposed to the air in contact with 
water it becomes entirely converted into Prussian blue. This interesting 
substance was discovered by Mr. Porrett. 

Ferrocyanide of potassium, frequently called Yellow prussiate of potash, 
K 2 Cfy-f3HO, or K 2 C 6 N 3 Fe-f 3HO.— This most beautiful salt is manufactured 
on a large scale by the following process, which will now be easily intelligi- 
ble : — Dry refuse animal matter of any kind is fused at a red-heat with im- 
pure carbonate of potassa and some iron-filings in a large iron vessel, from 
which the air should be excluded as much as possible; cyanide of potassium 
is generated in large quantity. The melted mass is afterwards treated with 
hot water, which dissolves out the cyanide and other salts ; the cyanide being 
quickly converted by the oxide or sulphide l of iron into ferrocyanide. The 
filtered solution is evaporated, and the first-formed crystals purified by re- 
solution. If a sufficient quantity of iron be not present, great loss is incurred 
by the decomposition of the cyanide into formate of potassa and ammonia. 

Ferrocyanide of potassium forms large, transparent, yellow crystals, 
derived from an octahedron with a square base ; they cleave with facility in 
a direction parallel to the base of the octahedron, and are tough and diffi- 
cult to powder. They dissolve in 4 parts of cold, and in 2 of boiling water, 
and are insoluble in alcohol. They are permanent in the air, and have a 
mild saline taste. The salt has no poisonous properties, and in small doses, 
at least, is merely purgative. Exposed to a gentle heat, it loses 3 eq. of 
water, and becomes anhydrous ; at a high temperature it yields cyanide of 
potassium, carbide of iron, and various gaseous products ; if air be ad- 
mitted, the cyanide becomes cyanate. 

The ferrocyanides are often described as double salts in which protocy- 
anide of iron is combined with other metallic cyanides, or with hydrogen. 
Thus, hydroferrocyanic acid is written FeCy,2HCy, and ferrocyanide of 
potassium, FeCy,2KCy-f-3HO; the oxygen and hydrogen of the water of 
crystallization being respectively adequate to convert the metals into pro- 
toxide and the cyanogen into hydrocyanic acid. This view has the merit of 
simplicity, and will often prove an useful aid to the memory, but there are 
insuperable objections to its adoption as a sound and satisfactory theory. 

Ferrocyanide of potassium is a chemical reagent of great value ; when 
mixed in solution with neutral or slightly acid salts of the metals proper, it 
gives rise to precipitates which very frequently present highly characteristic 
colours. In most of these compounds the potassium of the base is simply 
displaced by the new metal : the beautiful brown ferrocyanide of copper 
contains, for example, Cu 2 Cfy or Cu 2 C 6 N 3 Fe, and that of lead, Pb 2 Cfy. AVith 
salts of protoxide of iron it gives a bluish precipitate, which becomes 
rapidly dark blue by exposure to air ; this appears to be a compound of the 
neutral ferrocyanide of iron, Fe 2 Cfy, with ferrocyanide of potassium. 

When a ferrocyanide is added to a solution of salt of sesquioxide oi iron, 
Prussian blue is produced. Although this remarkable substance has now 
been long known, and many elaborate researches have been made with a 
view of determining its exact composition, the problem cannot yet be said 
to be completely solved. This difficulty arises in great measure from the 
existence of several distinct deep blue compounds formed under different cir- 

1 The sulphur is derived from the reduced sulphate of the crude pearl-ashes used in thi* 
manufacture. 



432 FERRO CYANOGEN AN D ITS COMPOUNDS. 

cumstances, and having many properties in common, which have been fre- 
quently confounded. The following is a summary of the account given by 
Berzelius, who has paid much attention to this subject. 

Ordinary Prussian Blue, C 18 N g Fe 7 , or Fe 4 Cfy 3 . — This is best prepared by 
adding nitrate of sesquioxide of iron to solution of ferrocyanide of potas- 
sium, keeping the latter in slight excess. It forms a bulky precipitate of 
the most intense blue, which shrinks to a comparatively small compass 
when well washed and dried by gentle heat. In a dry state it is hard and 
brittle, much resembling in appearance the best indigo ; the fresh-fractured 
surfaces have a beautiful copper-red lustre, similar to that produced by 
rubbing indigo with a hard body. Prussian blue is quite insoluble in water 
and dilute acids, with the exception of oxalic acid, in a solution of which it 
dissolves, forming a deep blue liquid, which is sometimes used as ink ; con- 
centrated oil of vitriol converts it into a white, pasty mass, which again 
becomes blue on the addition of water. Alkalis destroy the colour in- 
stantly ; they dissolve out a ferrocyanide, and leave sesquioxide of iron. 
Boiled with water and red oxide of mercury, it yields a cyanide of the 
metal, and sesquioxide of iron. Heated in the air, Prussian blue burns 
like tinder, leaving a residue of sesquioxide of iron. Exposed to a high 
temperature in a close vessel, it disengages water, cyanide of ammonium, 
and carbonate of ammonia, and leaves carbide of iron. This substance 
forms a very beautiful pigment, both an oil and a water-colour, but has 
little permanency. The Prussian blue of commerce is always exceedingly 
impure ; it contains alumina and other matters, which greatly diminish the 
brilliancy of the colour. 

The production of Prussian blue by mixing sesquioxide salt of iron and 
ferrocyanide of potassium or sodium may thus be elucidated: — 

3 eq. ferrocyanide f 3 eq. ferrocyanogen — — ^- - Prussian blue. 

potassium \ 6 eq. potassium 

2 eq. nitrate of f 4 eq. iron 

sesquioxide of < 6 eq. oxygen 

iron (. 6 eq. nitric acid "^ 6 eq. nitrate of po- 

tassa. 

In the above formula no account is taken of the elements of water which 
Prussian blue certainly contains ; in fact it must be looked upon as still 
requiring examination. 

The theory of the beautiful test of Scheele for the discovery of hydrocy- 
anic acid, or any soluble cyanide, will now be clearly intelligible. The 
liquid is mixed with a salt of protoxide of iron and excess of caustic alkali ; 
the protoxide of iron quickly converts the alkaline cyanide into ferrocy- 
anide. By exposure for a short time to the air, another portion of the 
hydrated oxide becomes peroxidized ; when excess of acid is added, this is 
dissolved, together with the unaltered protoxide ; and thus presented to the 
ferrocyanide in a state fitted for the production of Prussian blue. 

Basic Prussian Blue, Fe 4 Cfy 3 -f-Fe 2 3 . — This is a combination of Prussian 
blue with sesquioxide of iron; it is formed by exposing to the air the white 
or pale blue precipitate caused by a ferrocyanide in a solution of protosalt 
of iron. It differs from the preceding in being soluble in pure water, 
although not in a saline solution. 

The blue precipitate obtained by adding nitrate of sesquioxide of iron to 
a large excess of ferrocyanide of potassium, is a mixture of insoluble 
Prussian blue with a compound containing that substance in union witli fer- 
rocyanide of potassium, or Fe 4 Cfy 3 -j-2K 2 Cfy. This also dissolves iu water 
as soon as the salts have been removed by washing. 




FERRICYANOGEN AND ITS COMPOUNDS. 433 

The other ferrocyanides may be despatched in a few -words. 

The soda-salt, Na 2 Cfy-|-12HO, crystallizes in yellow four-sided prisms, 
which are efflorescent in the air and very soluble. 

Ferrocyanide of ammonium, (NH 4 )C 2 fy-f-oHO, is isomorphous with ferro- 
cyanide of potassium ; it is easily soluble, and is decomposed by ebullition. 
Ferrocyanide of barium, Ba 2 Cfy, prepared by double decomposition, or by 
boiling Prussian blue in baryta-water, forms minute yellow, anhydrous crys- 
tals, which have but a small degree of solubility even in boiling water. The 
corresponding compounds of strontium, calcium, and magnesium, are more 
freely soluble. The ferrocyanides of silver, lead, zinc, manganese, and bis- 
muth are white and insoluble ; those of nickel and cobalt are pale green, and 
insoluble ; and, lastly, that of copper has a beautiful reddish-brown tint. 

Ferrocyanides with two basic metals are occasionally met with ; when, for 
example, concentrated solutions of chloride of calcium and ferrocyanide of 
potassium are mixed, a sparingly-soluble crystalline precipitate falls, con- 
taining KCaCfy, the salt-radical being half saturated with potassium, and 
half with calcium ; many similar compounds have been formed. 

Ferri-, or ferrldcyanogen, C 12 N 6 Fe 2 ; or Cfcly. — This name is given to 
a substance, by some thought to be a new salt-radical, isomeric with ferro- 
cyanogen, but diifering in capacity of saturation ; it has never been isolated. 
Ferricyanide of potassium is thus prepared: — Chlorine is slowly passed, with 
agitation, into a somewhat dilute and cold solution of ferrocyanide of potas- 
sium, until the liquid acquires a deep reddish-green colour, and ceases to 
precipitate a salt of the sesquioxide of iron. It is then evaporated until a 
skin begins to form upon the surface, filtered, and left to cool ; the salt is 
purified by re-crystallization. It forms regular prismatic, or sometimes 
tabular crystals, of a beautiful ruby-red tint, permanent in the air, and solu- 
ble in 4 parts of cold water ; the solution has a dark greenish colour. The 
crystals burn when introduced into the flame of a candle, and emit sparks. 

Ferricyanide of potassium contains K 3 Cfdy ; hence the radical is tribasic ; 
the salt is formed by the abstraction of an equivalent of potassium from 2 
eq. of the yellow ferrocyanide of potassium. It is decomposed by excess 
of chlorine, and by deoxidizing agents, as sulphuretted hydrogen. The 
term red prussiate of potash is often, but very improperly, given to this sub- 
stance. 

Ferricyanide of hydrogen is obtained in the form of a reddish-brown acid 
£quid, by decomposing ferricyanide of lead with sulphuric acid ; it is very 
instable, and is resolved, by boiling, into a hydrated sesquicyanide of iron, 
an insoluble dark green powder, containing Fe 2 Cy 3 -f-8HQ, and hydrocyanic 
acid. The ferrieyanides of sodium, ammonium, and of the alkaline earths, 
are soluble ; those of most of the other metals are insoluble. Ferricyanide 
of potassium, added to a salt of the sesquiozide of iron, occasions no precipi- 
tate, but merely a darkening of the reddish-brown colour of the solution ; 
with protoxide of iron, on the other hand, it gives a deep blue precipitate, 
containing Fe 3 Cf dy, which, when dry, has a brighter tint than that of Prus- 
sian blue; it is known under the name of TurnbuWs blue. Hence, ferri- 
cyanide of potas&lum is as excellent a test for protoxide of iron, as the yellow 
ferrocyanide is for the sesquioxide. 

Cobaltocyanogen. — A series of compounds analogous to the preceding, 
containing cobalt in place of iron, have been formed and studied ; a hydro- 
gen-acid has been obtained and a number of salts, which much resemble 
those of ferricyanogen. Several other metals of the same isomorphous 
family are found capable of replacing iron in these circumstances. 

Nitroprussides. — The action of nitric acid upon ferrocyanides and fern- 
cyanides gives rise to the formation of a very interesting series of new salts, 
which were discovered by Dr. Playfair. The general formula of these salts 
37 



434 SULPHOCYANOGEN, ITS COMPOUNDS. 

appears to be M 2 Fe 2 Cy 5 NO, winch exhibits a close relation with th(*e of the 
ferro- and ferricyanides. 

2M 2 Cfy = M 4 Fe 2 Cy = ferrocyanides. 
2>I 3 Fe 2 Cy 6 = ferricyanides. 

N ^ = nitroprussides. 

According to this formula, the formation of the nitroprusside would con- 
sist in the reduction of the nitric acid to the state of protoxide of nitrogen, 
which replaces 1 eq. of cyanogen in 2 eq. of ferrocyanide. The formation 
of these salts is attended by the production of a variety of secondary pro- 
ducts, such as cyanogen, oxamide, hydrocyanic acid, nitrogen, carbonic acid, 
&c. One of the finest compounds of this series is the nitroprusside of 
sodium, Na 2 *FeCy 5 NO-|-4IIQ, w hi c h is readily obtained by treating 2 parts 
of the powdered ferrocyanide with 5 parts of common nitric acid, previously 
diluted with its own volume of water. The solution, after the evolution of 
gas has ceased, is digested on the water-bath, until salts of protoxide of iron 
no longer yield a blue but a slate-coloured precipitate. The liquid is now 
allowed to cool, when much nitrate of potassa, and occasionally oxamide, is 
deposited ; it is filtered and neutralized with carbonate of soda, which yields 
a green or brown precipitate, and furnishes a ruby-coloured filtrate. This, 
on evaporation, gives a crystallization of nitrate of potassa and soda, toge- 
ther with the new salt. The crystals of the latter are selected and purified 
by crystallization ; they are rhombic, and of a splendid ruby colour. The 
soluble nitroprussides strike a most beautiful violet tint with soluble sul- 
phides. This reaction is recommended by Dr. Plavfair as the most delicate 
test for alkaline sulphides. 

SULPHOCYANOGEN, ITS COMPOUNDS AND DERIVATIVES. 

The elements of cyanogen combine with sulphur, forming a very important 
and well-defined salt-radical, called mlpho cyanogen, which contains C 2 NS 2 , 
and is monobasic ; it is expressed by the symbol Csy. 

Sulphocyanide of potassium, KCsy. — Yellow ferrocyanide of potassium, 
deprived of its water of crystallization, is intimately mixed with half its 
weight of sulphur, and the whole heated to tranquil fusion in an iron pot, 
and kept some time in that condition. "When cold, the melted mass is boiled 
with water, which dissolves out a mixture of sulphocyanide of potassium and 
sulphocyanide of iron, leaving little behind but the excess of sulphur em- 
ployed in the experiment. This solution, which becomes red on exposure to 
the air from the oxidation of the iron, is mixed with carbonate of potassa, by 
which the oxide of iron is precipitated, and potassium substituted ; an excess 
of the carbonate must be, as far as possible, avoided. The filtered liquid is 
concentrated, by evaporation over an open fire, to a small bulk, and left to 
cool and crystallize. The crystals are drained, purified by re-solution, if 
necessary, or dried by inclosing them, spread on filter-paper, over a surface 
of oil of vitriol, covered by a bell-jar. 

The reaction between the sulphur and the elements of the yellow salt is 
easily explained : 1 eq. of ferrocyanide of potassium, and G eq. sulphur, 
yielded 2 eq. of sulphocyanide of potassium, and 1 eq. of sulphocyanide of 
iron. 

K 2 Cfy=C 6 N 3 Fe,K 2 -{-6S=2(KC 2 NS 2 )-f-FeC 2 NS 2 . 

Another and perhaps simpler process consists in gradually heating to low 
redness in a covered vessel a mixture of 46 parts of dried ferrocyanide of 



SULPHOCYANOGEN, ITS COMPOUNDS. 4oO 

potassium, 32 of sulphur, and 17 of pure carbonate of potassa. The mass is 
exhausted by water, the aqueous solution evaporated to dryness and ex- 
tracted with alcohol. The alcoholic liquid deposits splendid crystals on cool- 
ing or evaporation. 

The new salt crystallizes in long, slender, colourless prisms, or plates, 
which are anhydrous ; it has a bitter, saline taste, and is destitute of poi- 
sonous properties ; it is very soluble in water and alcohol, and deliquesces 
when exposed to a moist atmosphere. When heated, it fuses to a colourless 
liquid, at a temperature far below that of ignition. 

"When chlorine is passed into a strong solution of sulphocyanide of potas- 
sium, a large quantity of a bulky, deep yellow, insoluble substance, resem- 
bling some varieties of chromate of lead, is produced, together with chloride 
of potassium, which tends to choke up the tube delivering the gas ; the liquid 
sometimes assumes a deep red tint, and disengages a pungent vapour, pro- 
bably chloride of cyanogen. This yellow matter may be collected on a filter, 
well washed with boiling water, and dried : it retains its brilliancy of tint. 
The term sulpho cyanogen has generally been applied to this substance, from 
its supposed identity with the radical of the sulphocyanides ; it is, however, 
invariably found to contain both oxygen and hydrogen, and a formula much 
more complex than that belonging to the true sulphocyanogen, namely C 8 H 2 
N 4 S 8 0, has been lately assigned to it. The yellow substance is quite insoluble 
in water, alcohol, and ether; it dissolves in concentrated sulphuric acid, 
from which it is precipitated by dilution. Caustic potassa also dissolves it, 
with decomposition ; acids throw down from this solution a pale yellow, 
insoluble body, having acid properties. When heated in a dry state, the 
so-called sulphocyanogen evolves sulphur and bisulphide of cai^bon, and 
leaves a curious, pale straw-yellow substance, called mellon, which coniaius 
C 6 N 4 , and is known to combine with hydrogen and the metals. Mellon bears 
a dull red-heat without decomposition, but is resolved by strong ignition into 
a mixture of cyanogen and nitrogen gases. It is quite insoluble in water ; 
alcohol, and dilute acids. 

Hydrostilphocyanic acid, HCsy, is obtained by decomposing sulphocya- 
nide of lead, suspended in water, by sulphuretted hydrogen. The filtered 
solution is colourless, very acid, and not poisonous ; it is easily decomposed, 
in a very complex manner, by ebullition ; and by exposure to the air. By 
neutralizing the liquid with ammonia, and evaporating very gently, to dry- 
ness, sulphocyanide of ammonium, NH 4 Csy, is obtained as a deliquescent, 
saline mass. This salt may be conveniently prepared by digesting hydro- 
cyanic acid with yellow sulphide of ammonium, and boiling oif the excess of 
the latter (NH 4 S 3 +HCy=NH 4 Csy-|-HS). The sulphocyanides of sodium, 
barium, strontium, calcium, manganese, and iron are colourless, and very 
soluble ; those of lead and silver are white and insoluble. A soluble sulpho- 
cyanide, mixed with a salt of the sesquioxide of iron, gives no precipitate 
but causes the liquid to assume a deep blood-red tint, exactly similar to that 
caused under similar circumstances by meconic acid ; hence the occasional 
use of sulphocyanide of potassium as a test for iron in the state of sesqui- 
oxide. The great facility with which hydrocyanic acid may be converted 
into sulphocyanide of ammonium enables us to ascertain the presence by the 
iron-test just described. The cyanide to be examined is mixed in a watch- 
glass with some hydrochloric acid and covered with another watch-glass, to 
which a few drops of yellow sulphide of ammonium adhere. On heating the- 
mixture, hydrocyanic acid is disengaged, which combines with the sulphide 
of ammonium, and produces sulphocyanide of ammonium ; this, after the 
expulsion of the excess of sulphide, yields the red colour -with solution of 
sesquioxide of iron. 

Selenocyanogen. — A series of salts containing selenium, and corresponding 



430 urea; uric acid and its products. 

in their composition and properties with sulphocyanides, exist. They have 
been lately studied by Mr. Crookes. 

Melam. — Such is the name given by Liebig to a curious buff-coloured, 
insoluble, amorphous substance, obtained by the distillation at a high tem- 
perature of sulphocyanide of ammonium. It may be prepared in large 
quantity by intimately mixing 1 part of perfectly dry sulphocyanide of po- 
tassium with 2 parts of powdered sal-ammoniac, and heating the mixture 
for some time in a retort or flask ; bisulphide of carbon, sulphide of ammo- 
nium, and sulphuretted hydrogen are disengaged and volatilized, while a 
mixture of melam, chloride of potassium, and some sal-ammoniac remains ; 
the two latter substances are removed by washing with hot water. Melam 
contains C ]2 H 9 N n ; it dissolves in concentrated sulphuric acid, and gives, by 
dilution with water and long boiling, cyanuric acid. The same substance is 
produced with disengagement of ammonia when melam is fused with hydrate 
of potassa. When strongly heated, melam is resolved into mellon and 
ammonia. 

If melam be boiled for a long time in a moderately strong solution of 
caustic potassa, until the whole has dissolved, and the liquid be then concen 
trated, a crystalline substance separates on cooling, which is called melamine, 
By re-crystallization it is obtained in colourless crystals, having the figure 
of an octahedron with rhombic base ; it is but slightly soluble in cold water, 
fusible by heat, and volatile with trifling decomposition. It contains C 6 H 6 N C , 
and acts as a base, combining with acids to crystallizable compounds. A 
second basic substance called ammeline, very similar in properties to mela- 
mine, is found in the alkaline mother-liquor from which the melamine has 
separated ; it is thrown down on neutralizing the liquid with acetic acid. 
The precipitate, dissolved in dilute nitric acid, yields crystals of nitrate of 
ammeline, from which the pure ammeline may be separated by ammonia. It 
forms a brilliant white powder of minute needles, insoluble in water and 
alcohol, and contains C 6 H 5 N 5 2 . "When ammeline is dissolved in concentrated 
sulphuric acid, and the solution mixed with a large quantity of water, or, 
better, spirit of wine, a white, insoluble powder falls, which is designated 
ammelide, and is found to contain C ]2 H 9 N 9 6 . When long boiled with dilute 
sulphuric acid, melamine, ammeline, and ammelide are converted into cya- 
nuric acid and ammonia. 

UREA ; URIC ACID AND ITS PRODUCTS. 

These bodies are closely connected with the cyanogen-compounds, and may 
be most conveniently discussed in the present place. 

Urea. — Urea may be extracted from its natural source, the urine, or it 
may be prepared by artificial means. Fresh urine is concentrated in a 
water-bath, until reduced to an eighth or a tenth of its original volume, and 
filtered through cloth from the insoluble deposit of urates and phosphates. 
The liquid is mixed with about an equal quantity of a strong solution of 
oxalic acid in hot water, and the whole vigorously agitated and left to cool. 
A very copious fawn-coloured crystalline precipitate of oxalate of urea is 
obtained, which may be placed upon a cloth filter, slightly washed with cold 
water, and pressed. This is to be dissolved in boiling-hot water, and pow- 
dered chalk added until effervescence ceases, and the liquid becomes neutral. 
The solution of urea is filtered from the insoluble oxalate of lime, warmed 
with a little animal charcoal, again filtered, and concentrated by evaporation, 
avoiding ebullition, until crystals form on cooling; these are purified by a 
repetition of the last part of the process. Urea can be extracted in great 
abundance from the urine of horses and cattle, duly concentrated, and from 
which the hippuric acid has been separated by the addition of hydrochloric 
acid; oxalic acid then throws down the oxalate in such quantity as to render 



urea; uric acid and its products. 437 

the whole serai-solid. Another process consists in precipitating the evapo- 
rated urine with concentrated nitric acid, when nitrate of urea is precipitated, 
which is re-crystallized with animal charcoal, and lastly decomposed by car- 
bonate of baryta. A mixture of nitrate of baryta and urea is formed, which 
is evaporated to dryness on the water-bath, and exhausted with alcohol, from 
which the urea crystallizes on cooling. 

By artificial means, urea is produced by heating solution of cyanate of 
ammonia. The following method of proceeding yields it in any quantity 
that can be desired. Cyanate of potassa, prepared by Liebig's process, 1 is 
dissolved in a small quantity of water, and a quantity of dry neutral sulphate 
of ammonia, equal in weight to the cyanate, added. The whole is evapo- 
rated to di'yness in a water-bath, and the dry residue boiled with strong 
alcohol, which dissolves out the urea, leaving the sulphate of potassa and 
the excess of sulphate of ammonia untouched. The filtered solution, con- 
centrated by distilling off a portion of the spirit, deposits the urea in beau- 
tiful crystals of considerable magnitude. 

Urea forms transparent, colourless, four-sided prisms, which are soluble 
in an equal weight of cold water, and in a much smaller quantity at a high 
temperature. It is also readily dissolved by alcohol. It is inodorous, has 
a cooling, saline taste, and is permanent in the air, unless the latter be very 
damp. When heated, it melts, and at a higher temperature, decomposes with 
evolution of ammonia and cyanate of ammonia ; cyanuric acid remaius, which 
bears a much greater heat without change. The solution of urea is neutral 
to test-paper ; it is not decomposed in the cold by alkalis or by hydrate of 
lime, but at a boiling heat emits ammonia, and forms a carbonate of the 
base. The same change happens by fusion with the alkaline hydrates. 
Brought into contact with nitrous acid, it is decomposed instantly into a 
mixture of nitrogen and carbonic acid gases ; this decomposition explains 
the use of urea in preparing nitric ether (see page 351). With chlorine it 
yields hydrochloric acid, nitrogen, and carbonic acid. Crystallized urea is 
anhydrous; it contains ^r^XgC^, or the elements of cyanate of oxide of ammo- 
nium. It differs from carbonate of ammonia by the elements of water ; hence 
it might with some propriety be called carbamide. It is easily converted into 
carbonate of ammonia by assimilating the oxygen and hydrogen of 2 eq. of 
water. A solution of pure urea shows no tendency to change by keeping, 
and is not decomposed by boiling ; in the urine, on the other hand, where 
it is associated with putrefiable oi'ganic matter, as mucus, the case is diffe- 
rent. In putrid urine no urea can be found, but enough carbonate of 
ammonia to cause brisk effervescence with an acid ; and if urine, in a recent 
state, be long boiled, it gives off ammonia and carbonic acid from the same 
source. 

Urea acts as a salt-base ; with nitric acid it forms a sparingly soluble 
compound, which crystallizes, when pure, in small, indistinct, colourless 
plates, containing single equivalents of urea, nitric acid, and water. When 
colourless nitric acid is added to urine, concentrated to a fourth or a sixth 
of its volume, and cold, the nitrate crystallizes out in large, brilliant, yellow 
lamina?, which are very insoluble in the acid liquid. The production of 
this nitrate is highly characteristic of urea. The oxalate, when pure, crys- 
tallizes in large, transparent, colourless plates, which have an acid reaction, 
and are sparingly soluble ; it contains an equivalent of water. Urea forms 
several compounds with metallic salts, e. g., with those of mercury. On 
mixing a liquid containing urea with a solution of nitrate of protoxide of 
mercury, a white precipitate takes place, which is a compound of urea with 
4 eq. of protoxide of mercury. If the nitric acid which is thus set free, be 

1 See page 427. 

37* 



438 URIC ACID AND ITS PRODUCTS. 

neutralized by the addition of an alkali or baryta-water, the whole of the 
urea is removed from the liquid in the form of the above compounds. Prof. 
Liebig, to whom we are indebted for this observation, has based upon this 
deportment a process of determining the amount of urea in urine. The de- 
tails of this method, which is equally interesting to the chemist and the 
physiologist, have not yet been published. 

A series of substances analogous to urea, which have lately been disco- 
vered and described under the name of methylamine-urea, ethylamine-urea, 
biethylamine-urea, &c, will be noticed in the section on the vegeto-alkalis. 
Uric, or lithic acid. — This is a product of the animal organism, and has 
never been formed by artificial means. It may be prepared from human 
urine by concentration, and addition of hydrochloric acid ; it crystallizes 
out after some time in the form of small, reddish, translucent grains, very 
difficult to purify. A much preferable method is, to employ the solid white 
excrement of serpents, which can be easily procured; this consists almost 
entirely of uric acid and urate of ammonia. It is reduced to powder, and 
boiled in dilute solution of caustic potassa ; the liquid, filtered from the in- 
significant residue of feculent matter, and earthy phosphates, is mixed with 
excess of hydrochloric acid, boiled for a few minutes, and left to cool. The 
product is collected on a filter, washed until free from chloride of potassium, 
and dried by gentle heat. 

Uric acid, thus obtained, forms a glistening, snow-white powder, tasteless, 
inodorous, and very sparingly soluble. It is seen 
under the microscope to consist of minute, but 
regular crystals (fig. 173). It dissolves in concen- 
trated sulphuric acid without apparent decomposi- 
tion, and is precipitated by dilution with water. 
By destructive distillation, uric acid yields cyanic, 
hydrocyanic, and carbonic acids, carbonate of am- 
monia, and a black coaly residue, rich in nitrogen. 
By fusion with hydrate of potassa, it furnishes 
carbonate and cyanate of the base, and cyanide of 
'" m C\ ^~^ *ke alkaline metal. When treated with nitric acid 
*Qjy \»J Q and with binoxide of lead, it undergoes decomposi- 

tion in a manner to be presently described. 
Uric acid is found by analysis to contain C 10 H 2 N 4 O 4 ,2HO. It is a bibasic 
acid. 

The only salts of uric acid that have attracted any attention are those of 
the alkalis; acid urate of potassa contains KO,HO,C I0 H 2 N 4 O 4 ; it is deposited 
from a hot, saturated solution of uric acid in the dilute alkali as a white, 
sparingly soluble concrete mass, composed of minute neeJles ; it requires 
about 500 parts of cold water for solution, is rather more soluble at a high 
temperature, and much more soluble in excess of alkali. Urate of soda re- 
sembles the salt of potassa ; it forms the chief constituent of the gouty con- 
cretions in the joints, called chalk-stones. Urate of ammonia is also a sparingly 
soluble compound, requiring for the purpose about 1000 parts of cold water ; 
the solubility is very much increased by the presence of a small quantity of 
certain salts, as chloride of sodium. This is the most common of the urinary 
deposit;;, forming a buif-coloured or pinkish cloud or muddiness, which dis- 
appears by re-solution when the urine is warmed; the secretion from which 
this is deposited has an acid reaction. It occurs also as a calculus. 

The following substances result from the oxidation of uric acid by binoxide 
of lead and nitric acid ; they are some of the most beautiful and interesting 
bodies known, most of which have been discovered by Liebig and Wohler. 

Allaktoin. — Allantoin occurs ready formed in the allantoic liquid of the 
foetal calf. It is produced artificially by boiling together water, uric acid, 




URIC ACID AND ITS PRODUCTS. 439 

and pure, freshly prepared binoxide of lead ; the filtered liquid, duly concen- 
trated by evaporation, deposits crystals of allantoin on cooling, which are 
purified by re-solution and the use of animal charcoal. It forms small but 
most brilliant prismatic crystals, which are transparent and colourless, des- 
titute of taste, and without action on vegetable colours. Allantoin dissolves 
in 160 parts of cold water, and in a small quantity at the boiling temperature. 
It is decomposed by boiling with nitric acid, and by oil of vitriol when con- 
centrated and hot, being in this case resolved into ammonia, carbonic acid, 
and carbonic oxide. Heated with concentrated solution of caustic alkalis, it 
is decomposed into ammonia and oxalic acid, which latter combines with the 
base. These reactions are explained by the analysis of the substance, which 
shows it to be composed of the elements of oxalate of ammonia minus those 
of three equivalents of water, or C 4 H 3 N 2 3 . 

The production of allantoin from uric acid and binoxide of lead is also per- 
fectly intelligible ; 1 eq. of uric acid, 2 eq. of oxygen from the binoxide, and 
3 eq. of water, contain the elements of allantoin, 2 eq. of oxalic acid, and 1 
eq. of urea. 

C 10 H 4 N 4 O 6 +2O\ _ f C 4 H 3 N 2 3 +2(HO,C 2 3 ) 
+ 3HO / — I 4- C 2 H 4 N 2 2 . 

The insoluble matter from which the solution of allantoin is filtered con- 
sists in great part of oxalate of lead, and the mother-liquor from which the 
crystals of allantoin have separated, yields, on farther evaporation, a large 
quantity of pure urea. 

Alloxan. — This is the characteristic product of the action of concentrated 
nitric acid on uric acid in the cold. An acid is prepared, of sp. gr. 1-45, or 
thereabouts, and placed in a shallow open basin ; into this a third of its 
weight of dry uric acid is thrown, by small portions, with constant agitation, 
care being taken that the temperature never rises to any considerable extent. 
The uric acid at first dissolves with copious effervescence of carbonic acid 
and nitrogen, and eventually, the whole becomes a mass of white, crystal- 
line, pasty matter. This is left to stand some hours, drained from the acid 
liquid in a funnel whose neck is stopped with powder and fragments of glass, 
and afterwards more effectually dried upon a porous tile. This is alloxan in 
a crude state ; it is purified by solution in a small quantity of water, and 
crystallization. 

Alloxan crystallizes with facility from a hot and concentrated solution, 
slowly suffered to cool, in solid, hard, anhydrous crystals of great regularity, 
which are transparent, nearly colourless, have a high lustre, and the figure 
of a modified rhombic octahedron. A cold solution, on the other hand, left 
to evaporate spontaneously, deposits large foliated crystals, which contain 6 
eq. of water ; they effloresce rapidly in the air. Alloxan is very soluble in 
water ; the solution has an acid reaction, a disagreeable astringent taste, and 
stains the skin, after a time, red or purple. It is decomposed by alkalis, and 
both by oxidizing and de-oxidizing agents ; its most characteristic property 
is that of forming a deep blue compound with a salt of protoxide of iron and 
an alkali. 

Alloxan contains C 8 H 4 N 2 O 10 ; its production is thus illustrated : 1 eq. of 
uric acid, 4 eq. of water, and 2 eq. of nitric acid, contain the elements of 
alloxan, 2 eq. carbonic acid, 2 eq. of free nitrogen, 1 eq. of nitrate of am- 
monia: — 

C io" 4 N 4^6 + 2HO ") p TT TST O -4-2CO -UN -LNH O NO 

I 2(HO,NO ) / ^8 n 4^2 yj }0H- Z ^ KJ 2-t-]y 2 H- j}irl 4 KJ ,j.\KJ s . 

When to a solution of alloxan, heated to 140° (60°C), baryta-water is added 
as long as the precipitate first produced re-dissolves, and the filtered solution 



440 URIC ACID AND ITS PRODUCTS. 

is then left to cool, a substance is deposited in small, colourless, pearly crys- 
tals, which consists of baryta in combination with a new acid, the alloxanic. 
From this salt the base may be separated by the cautious addition of dilute 
sulphuric acid : the filtered liquid by gentle evaporation yields alloxanic acid 
in small radiated needles. It has an acid taste and reaction, decomposes car- 
bonates, and dissolves zinc with disengagement of hydrogen. It is a bibasiG 
acid, and contains in the hydrated state C s H 2 N 2 8 ,2HO ; hence it is isomeric 
with alloxan. The alloxanates of the alkalis are freely soluble ; those of the 
earths dissolve in a large quantity of tepid water, and that of silver is quite 
insoluble and anhydrous. 

If a warm saturated solution of alloxanate of baryta is heated to ebullition, 
a precipitate falls, which is a mixture of carbonate and alloxanate of baryta 
with an insoluble salt of a second new acid, the mesoxalic; the solution is 
found to contain unaltered alloxanate of baryta and urea. Mesoxalic acid 
is best prepared by slowly adding solution of alloxan to a boiling-hot solution 
of acetate of lead ; the heavy granular precipitate of mesoxalate of lead thus 
produced is washed and decomposed by sulphuretted hydrogen ; urea is also 
formed in this experiment. Hydrate of mesoxalic acid is crystallizable ; it 
has a sour taste and powerfully acid reaction, and resists a boiling heat; it 
forms sparingly soluble salts with baryta and lime, and a yellowish insoluble 
compound with oxide of silver, which is reduced with effervescence when 
gently heated. This remarkable acid contains as hydrate C 3 4 ,2HO, and is 
consequently bibasic ; it is formed by the resolution of alloxan into urea, and 
2 eq. of mesoxalic acid : — 

C 8 H 4 N 2 O 10 -f2HO=C 2 H 4 N 2 O 2 +2(HO,C 3 O 4 ). 

When ammonia in excess is added to a solution of alloxan, the whole 
heated to ebullition, and afterwards supersaturated with dilute sulphuric 
acid, a yellow, light precipitate falls, which increases in quantity as the liquid 
cools. This is mykomelinic acid; it is but feebly soluble in water, easily dis- 
solved by alkalis, and forms a yellow compound with oxide of silver. Myko- 
melinic acid contains C 8 II 5 N 4 5 ; it is produced by the conversion of alloxan 
and 2 eq. of ammonia into 1 eq. of mykomelinic acid and 5 eq. of water. 

Parabanic Acid. — This is the characteristic product of the action of 
moderately strong nitric acid on uric acid or alloxan, by the aid of heat; it 
is conveniently prepared by heating together 1 part of uric acid and 8 parts 
of nitric acid until the reaction has nearly ceased ; the liquid is evaporated 
to a syrupy state, and left to cool ; the acid is drained from the mother- 
liquid and purified by re-crystallization. Parabanic acid forms beautiful 
colourless, transparent, thin, prismatic crystals, which are permanent in the 
air ; it is easily soluble in water, has a pure and powerful acid taste, and 
reddens litmus strongly. Neutralized with ammonia, and mixed with nitrate 
of silver, it gives a white precipitate. Crystallized parabanic acid contains 
C 6 N 2 4 ,2HO ; its production is thus explained : 1 eq. of uric acid, 2 eq. of 
water, and 4 eq. of oxygen from the nitric acid, yield 1 eq. of parabanic 
acid, 4 eq. of carbonic acid, and 2 eq. of ammonia ; or, alloxan and four 
additional equivalents of oxygen furnish 1 eq. of parabanic acid, 2 eq. of 
cai'bonic acid, and 4 eq. of water. 

The alkaline parabanates undergo a singular change by exposure to heat ; 
if a solution of the acid be saturated with ammonia, boiled for a moment, 
and then left to cool, a substance separates in tufts of beautiful colourless 
needles ; this is the ammonia-salt of an acid called the oxaluric. The hy- 
drated acid is procured by adding an excess of dilute sulphuric acid to a hot 
and strong solution of oxalurate of ammonia, and cooling the whole 
rapidly It forms a white, crystalline powder, of acid taste and reaction, 
capable of combining with bases : the salts of baryta and lime are sparingly 



URIC ACID AND ITS PRODUCTS. 441 

soluble ; that of silver crystallizes from the mixed hot solution of nitrate of 
silver and oxalurate of ammonia in long, silky needles. Oxaluric acid is 
composed of C 6 H 3 N 2 7 ,HO; or the elements of 1 eq. of parabanic acid and 
3 eq. of water. A solution of oxaluric acid is resolved by ebullition into 
free oxalic acid and oxalate of urea. 

Thionuric acid. — A cold solution of alloxan is mixed with a saturated 
solution of sulphurous acid in water, in such quantity that the odour of the 
gas remains quite distinct ; an excess of cai'bonate of ammonia mixed with 
a little caustic ammonia is then added, and the whole boiled for a few 
minutes. On cooling, thionurate of ammonia is deposited in great abundance, 
forming beautiful colourless, crystalline plates, which by solution in water 
and re-crystallization acquire a fine pink tint. A solution of this salt gives 
with acetate of lead a precipitate of insoluble thionurate of the oxide of 
that metal, which is at first white and gelatinous, but shortly becomes dense 
aud crystalline : from this compound the hydrated acid may be obtained by 
the aid of sulphuretted hydrogen. It forms a white, crystalline mass, per- 
manent in the air, very soluble in water, of acid taste and reaction, and 
capable of combining directly with bases. When its solution is heated to 
the boiling-point, it undergoes decomposition, yielding sulphuric acid and a 
very peculiar and nearly insoluble substance, called uramile. Thionuric acid 
is bibasic ; the hydrate contains C 8 H 5 N 3 S 2 0] 2 ,2HO ; or the elements of 
alloxan, an equivalent of ammonia, and 2 eq. of sulphurous acid. 

Uramile. — The product of the decomposition by heat of hydrated thionu- 
ric acid. Thionurate of ammonia is dissolved in hot water, mixed with a 
small excess of hydrochloric acid, and the whole boiled in a flask ; a white, 
crystalline substance begins in a few moments to separate, which increases 
in quantity until the contents of the vessel often become semi-solid ; this is 
uramile. After cooling, it is collected on a filter, washed with cold water to 
remove the sulphuric acid, and dried by gentle heat, during which it fre- 
quently becomes pinkish. Examined by a lens, it is seen to consist of 
minute acicular crystals. It is tasteless and nearly insoluble in water, but 
dissolves in ammonia and the fixed alkalis. The ammoniacal solution be- 
comes purple in the air. It is decomposed by strong nitric acid, alloxan 
and nitrate of ammonia being generated. Uramile contains C 8 H 5 N 3 6 ; or 
thionuric acid minus the elements of 2 eq. of sulphuric acid. 

Uramilic acid. — When a cold saturated solution of thionurate of ammo- 
nia is mixed with dilute sulphuric acid, and evaporated in a water-bath, 
instead of uramile, another substance, uramilic acid, is formed and deposited 
in slender, colourless prisms, soluble in 8 parts of cold water. Uramilic 
acid dissolves in concentrated sulphui'ic acid without apparent decomposi- 
tion ; it has a feeble acid taste and reaction, and combines with bases. The 
salts of the alkalis are easily soluble ; those of the earths much less so, and 
that of the oxide of silver is insoluble. Uramilic acid contains Ci 6 H, N 5 O 15 ; 
2 eq. of uramile and 3 eq. of water contain the elements of uramilic acid 
and T eq. of ammonia. It is a substance difficult of preparation. 

Alloxantin. — This is the chief product of the action of hot dilute nitric 
acid upon uric acid; the surest and best method of preparing it, however, 
is by passing a stream of sulphuretted-hydrogen gas through a moderately 
strong and cold solution of alloxan. The impure mother-liquid from which 
the crystals of alloxan have separated answers the purpose perfectly well - 
it is diluted with a little water, and a copious stream of gas transmitteu 
through it. Sulphur is deposited in large quantity, mixed with a ^white, 
crystalline substance, which is the alloxantin. The product is drained upon 
a filter, slightly washed, and then boiled in water ; the filtered solution 
deposits the alloxantin on cooling. Alloxantin forms small, four-sided, 
oblique rhombic prisms, colourless and transparent ; it is soluble with diffi- 
culty in cold water, but more freely at a boiling temperature. The solution 



442 URIC ACID AND ITS PRODUCTS. 

reddens litmus, gives with baryta-water a violet-coloured precipitate, which 
disappears on heating, and when mixed with nitrate of silver produces a 
black precipitate of metallic silver. Heated with chlorine or nitric acid, it 
is changed by oxidation to alloxan. The crystals become red when exposed 
to ammoniacal vapours, 
equivalent of hydrogen. 

This substance is readily decomposed ; when a stream of sulphuretted 
hydrogen is passed through a boiling solution, sulphur is deposited and an 
acid liquid produced, supposed to contain a new acid, to which the term 
dialuric is applied. When neutralized by ammonia it yields a salt which 
crystallizes in colourless silky needles, containing NH 4 0,C 8 N 2 4 -j- 3HO 
They become deep red when heated to 212° (100°C) in the air. A hot satu> 
rated solution of alloxantin mixed with a neutral salt of ammonia instantly 
assumes a purple colour, which however quickly vanishes, and the liquid 
becomes turbid from the formation of uramile ; the liquid is then found to 
contain alloxan and free acid. With oxide of silver, alloxatin disengages 
carbonic acid, reduces a portion of the metal, and converts the remainder 
of the oxide into oxalurate. Boiled with water and binoxide of lead, allox- 
antin gives urea and carbonate of lead. 

Murexide ; purpurate of ammonia of Dr. Protjt. — There are several 
different methods of preparing this magnificent compound. It may be made 
directly from uric acid, by dissolving that substance in dilute nitric acid, 
evaporating to a certain point, and then adding to the warm, but not boiling 
liquid, a very slight excess of ammonia. In this experiment alloxantin is 
first produced, which becomes afterwards partially converted into alloxan ; 
the presence of both is requisite to the production of murexide. This pro- 
cess is, however, very precarious, and often fails altogether. An excellent 
method is to boil for a few minutes in a flask a mixture of 1 part of dry 
uramile, 1 part of red oxide of mercury, and 40 parts of water, to which 
two or three drops of ammonia have been added ; the whole assumes in a 
short space of time an intensely deep purple tint, and when filtered boiling- 
hot, deposits, on cooling, splendid crystals of murexide, unmixed with any 
impurity. A third, and perhaps even still better process, is that of Dr. Gre- 
gory : 7 parts of alloxan and 4 parts of alloxantin are dissolved in 240 parts 
of boiling water, and the solution added to about 80 parts of cold, strong- 
solution of carbonate of ammonia ; the liquid instantly acquires such a depth 
of colour as to become opaque, and gives on cooling a large quantity of mu- 
rexide ; the operation succeeds best on a small scale. 

Murexide 1 crystallizes in small square prisms, which by reflected light 
exhibit a splendid green metallic lustre, like that of the wing-cases of the 
rose-beetle and other insects ; by transmitted light they are deep purple-red. 
It is soluble with difficulty in cold water, much more easily at a boiling tem- 
perature, and is insoluble in alcohol and ether. Mineral acids decompose it 
with separation of murexan, and caustic potassa dissolves it, with production 
of a most magnificent purple colour, which disappears when the solution is 
boiled. Murexide contains, according to Liebig and Wohler, C] 2 H 6 N 5 8 ; its 
production may be thus explained; 2 eq. of uramile and 3 eq. of oxygen 
from the protoxide of mercury give rise to murexide, 1 eq. of alloxanic 
acid, and 3 eq, of water. 

2C fe H 5 N 3 6 -f 30 = C 12 H 6 N 5 8 ,C 4 HN0 4 + 3110. 

Or, on the other hand, 1 eq. of alloxan, 2 eq. of alloxantin, and 4 eq. of 
ammonia, yield 2 eq. of murexide and 14 eq. of water. 

C 8 H 4 N 8 Oio + 2C 8 H 5 N 2 O 10 -f 4NH 3 = 2C 12 H 6 N 5 8 -f 14HO. 

' So called from the Tyriau dye, said to hav: been prepared from a species oimurex, a shell- 
Gsh 



XANTHIC OXIDE, &C. 443 

Murexan ; purpuric acid of Dr. Prout. — Liebig directs this substance 
to be prepared by dissolving murexide in caustic potassa, beating the liquid 
until the colour disappears, and then adding an excess of dilute suphuric 
acid. It separates in colourless or slightly yellowish scales, nearly insoluble 
in cold water. In ammonia it dissolves, and the solution acquires a purple 
colour by exposure to the air, the murexide being then produced. Murexan 
is said to contain C 6 H 4 N 2 5 . This substance, and its relation to murexide, 
require re-examination. 

A series of substances closely related to the derivatives of uric acid, will 
be noticed under the head of Caffeine (see page 450). 

Connected with uric acid by similarity of origin, but not otherwise, are 
two curious and exceedingly rare substances, called xanthic oxide and cystic 
oxide. 

Xanthic oxide was discovered by Dr. Marcet; it occurs >as an urinary cal- 
culus, of pale brown colour, foliated texture, and waxy lustre, and is ex- 
tracted by boiling the pulverized stone in dilute caustic potassa and precipi- 
tating by carbonic acid. The xanthic oxide falls as a white precipitate, which 
on drying becomes pale yellow, and resembles wax when rubbed. It is 
nearly insoluble in water and dilute acids. Its characteristic property is to 
dissolve without evolution of gas in nitric acid, and to give on evaporation a 
deep yellow residue, which becomes yellowish-red on the addition of ammonia 
or solution of potassa. Xanthic oxide gives on analysis C 5 H 2 N 2 2 . 

Cystic oxide. — Cystic oxide calculi, although very rare, are more freqaently 
met with than those of the preceding substance ; they have a pale colour, a 
concentric structure, and often a waxy external crust. The powdered cal- 
culus dissolves in great part without effervescence in dilute acids and alkalis, 
including ammonia ; the ammoniacal solution deposits, by spontaneous evapo- 
ration, small, but beautiful colourless crystals, which have the form of six- 
sided prisms and square tables. It forms a saline compound with hydro- 
chloric acid. Caustic alkalis disengage ammonia from this substance by 
continued ebullition. Cystic oxide contains sulphur ; it is composed of 
C 6 H 6 NS 2 4 . 

Uric acid is perfectly well characterized, even when in very small quantity, 
by its behaviour with nitric acid. A small portion heated with a drop or 
two of nitric acid in a small porcelain capsule dissolves with copious effer- 
vescence. When this solution is cautiously evaporated nearly to dryness, 
and, after the addition of a little water, mixed with a slight excess of am- 
monia, the deep red tint of murexide is immediately produced. 

Impure uric acid, in a remarkable state of decomposition, is now importe« 
into this country in large quantities, for use as a manure, under the nam* 
of guano or huano. It comes from the barren and uninhabited islets of tht 
western coast of South America, and is the production of the countless birds 
that dwell undisturbed in those regions. The people of Peru have used it 
for ages. Guano usually appears as a pale brown powder, sometimes with 
whitish specks; it has an extremely offensive odour, the strength of which, 
however, varies very much. It is soluble in great part in water, and the 
solution is found to be extremely rich in oxalate of ammonia, the acid having 
been generated by a process of oxidation. Guano also contains a peculiar 
ubstance called guanine, which closely corresponds with xanthic oxide. Like 
urea, it combines with acids, forming a series of crystallizable salts. Guanine 
contains C 10 H 6 N s O 2 . 



4 14 VEGETO -ALKALIS 



SECTION Y. 
THE VEGETO-ALKALIS. 



The vegeto-alkalis, or alkaloids, or organic bases, constitute a remarkable 
and most interesting group of bodies ; they are met with in various plants, 
always in combination with an acid, which is in many cases "of peculiar 
nature, not occurring elsewhere in the vegetable kingdom. They are, for 
the most part, sparingly soluble in water, but dissolve in hot alcohol, from 
which they often crystallize in a very beautiful manner on cooling. Several 
of them, however, are oily, volatile liquids. The taste of these substances, 
when in solution, is usually intensely bitter, and their action upon the animal 
economy exceedingly energetic. They ail contain a considerable quantity 
of nitrogen, and are very complicated in constitution, having high combining 
numbers. It is probable that these bodies are very numerous. 

None of the organic bases occurring in plants have yet been formed by 
artificial means ; analogous substances have, however, been thus produced. 

Morphine, or morphia. — This is the chief active principle of opium ; it 
is the best and most characteristic type of the group, and the earliest known, 
dating back to the year 1803. 

Opium, the inspissated juice of the poppy-capsule, is a very complicated 
substance, containing, besides morphine, a host of other alkaloids in very 
variable quantities, combined with sulphuric acid and an organic acid called 
the meconic. In addition to these, there are gummy, resinous, and colouring 
matters, caoutchouc, &c, besides mechanical impurities, as chopped leaves. 
The opium of Turkey is the most valuable, and contains the largest quantity 
of morphine ; that of Egypt and of India are considerably inferior. It has 
been produced in England of the finest quality, but at great cost. 

If ammonia be added to a clear, aqueous infusion of opium, a very abundant 
buff-coloured or brownish-white precipitate falls, which consists principally 
of morphine and narcotiue, rendered insoluble by the withdrawal of the acid. 
The product is too impure, however, for use. The chief difficulty in the 
preparation of these substances is to get rid of the colouring matter, which 
adheres with great obstinacy, re-dissolving with the precipitates, and being 
again in part thrown down when the solutions are saturated with an alkali. 
The following method, which succeeds well upon a small scale, will serve to 
give the student some idea of a process very commonly pursued when it is 
desired to isolate at once an insoluble organic base, and the acid with which 
it is in combination: — A filtered solution of* opium in tepid water is mixed 
with acetate of lead in excess : the precipitated meconate of lead is separated 
by a filter, and through the solution containing acetate of morphine, now 
freed to a considerable extent from colour, a stream of sulphuretted hydrogen 
is passed. The filtered and nearly colourless liquid, from which the lead 
has been thus removed, may be warmed to expel the excess of gas, once 
more filtered, and then mixed with a slight excess of caustic ammonia, which 
throws down the morphine and narcotine ; these may be separated by boiling 
ether, in which the latter is soluble. The meconate of lead, well washed, 



VEGETO-AL KALIS. 445 

suspended in water, and decomposed by sulphuretted hydrogen, yields solu- 
tion of meconic acid. 

Morphine and its salts are advantageously prepared, on the lar^. scale, by 
the process of Dr. Gregory. A strong infusion of opium is mixed with a 
solution of chloride of calcium, free from iron; meconate of lime, which is 
nearly insoluble, separates, while the hydrochloric acid is transferred to the 
alkaloids. By duly cencentrating the filtered solution, the hydrochlorate of 
morphine may be made to crystallize, while the narcotine, and other bodies, 
are left behind. Repeated recrystallization, and the use of animal charcoal, 
then suffice to whiten and purify the salt, from which the base may be pre- 
cipitated in a pure state by ammonia. Other processes have been proposed, 
as that of M. Thiboumery, which consists in adding hydrate of lime in excess 
to an infusion of opium, by which the meconic acid is rendered insoluble, 
while the morphine is taken up with ease by the alkaline earth. By exactly 
neutralizing the filtered solution with hydrochloric acid, the morphine is pre- 
cipitated, .but in a somewhat coloured state. 

Morphine, when crystallized from alcohol, forms small, but very brilliant 
prismatic crystals, which are transparent and colourless. It requires at least 
1000 parts of water for solution, tastes slightly bitter, and has an alkaline 
reaction. These effects are much more evident in the alcoholic solution. It 
dissolves in about 30 parts of boiling alcohol, and with great facility in dilute 
acids ; it is also dissolved by excess of caustic potassa or soda, but scarcely 
by excess of ammonia. When heated in the air, morphine melts, inflames 
like a resin, and leaves a small quantity of charcoal, which easily burns away. 

Morphine, in powder, strikes a deep bluish colour with neutral salts of 
sesquioxide of iron, decomposes iodic acid with liberation of iodine, and forma 
a deep yellow or red compound with nitric acid ; these reactions are by some 
considered characteristic. 

Crystalline morphine contains C 34 H 19 N0 6 -f-2HO. 

The most characteristic and best-defined salt of this substance is the 
hydrochlorate. It crystallizes in slender, colourless needles, arranged in tufts 
or stellated groups, soluble in about 20 parts of cold water, and in its own 
weight at a boiling temperature. The crystals contain 6 eq. of water. The 
sulphate, nitrate, and phosphate are crystallizable salts ; the acetate crystallizes 
with great difficulty, and is usually in the state of a dry powder. The arti- 
ficial meconate is sometimes prepared for medicinal use. 

Narcotine. — The marc, or insoluble portion of opium, contains much nar- 
cotine, which may be extracted by boiling with dilute acetic acid. From the 
filtered solution the narcotine is precipitated by ammonia, and afterwards 
purified by solution in boiling alcohol, and filtration through animal charcoal. 
Narcotine crystallizes in small, colourless, brilliant prisms, which are nearly 
insoluble in water. The basic powers of narcotine are very feeble ; it is des- 
titute of alkaline reaction, and, although freely soluble in acids, refuses, for 
the most part, to form with them crystallizable compounds. 

According to Dr. Blyth, narcotine contains C^gHgjNO^. 

Narcotine yields some curious products by the action of oxidizing agents, 
as a mixture of dilute sulphuric acid and binoxide of manganese, or a hot 
solution of bichloride of platinum. They have been chiefly studied by Wohler 
and Blyth, and lately also by Anderson. The most important of these is 
opianic acid, a substance forming colourless, prismatic, reticulated crystals, 
sparingly soluble in cold water, easily in hot. It melts when heated, but 
does not sublime. After fusion it becomes quite insoluble in dilute alkalis, 
but without change of composition. This acid forms crystallizable salts and 
an ether ; it contains C 20 H 9 O 9 HO. The ammonia-salt, by evaporation to dry- 
ness, yields a nearly white insoluble powder, called opiammon, containing 
C^HjgNO,^ convertible by strong acids into opianic acid and ammonia. Sul- 



446 VEGETO-ALKALIS. 

phurous acid yields with opianic acid two products containing sulphur. A 
mixture of binoxide of lead, opianic acid, and sulphuric acid gives rise to a 
crystallizable bibasic acid termed hemipinic acid, containing C 20 H g O 10 ,2HO. 
A basic substance, cotarnine, C^HjgNOe, is contained in the mother-liquor 
from which opianic acid has crystallized ; it forms a yellow crystalline mass, 
very soluble, of bitter taste, and feebly alkaline reaction. Its hydrochlorate 
is a well-defined salt. Another basic substance, narcogenine, was accidentally 
produced in an attempt to prepare cotarnine by bichloride of platinum. It 
formed large orange-coloured needles, and contained CggH^NOjo- 

Codeine. — Hydrochlorate of morphine, prepared directly from opium as 
in Gregory's process, contains codeine-salt. When dissolved in water, and 
mixed with a slight excess of ammonia, the morphine is precipitated, and 
the codeine left in solution. Pure codeine crystallizes, by spontaneous evapo- 
ration, in colourless transparent octahedrons; it is soluble in 80 parts of 
cold, and 17 of boiling water, has a strong alkaline reaction, and forms crys- 
tallizable salts. 

Codeine is composed of C 36 H 21 N0 6 . This has lately been the subject of a 
careful investigation by Dr. Anderson, who has prepared a great number of 
its derivatives, all of which establish the formula given. 

Trebaine or paramokphine. — This substance is contained in the preci- 
pitate formed by hydrate of lime in a strong infusion of opium in Thibou- 
m^ry's process for morphine. The precipitate is well washed, dissolved in 
dilute acid, and mixed with ammonia in excess, and the thebaine thrown 
down, crystallized from alcohol. It forms when pure colourless needles like 
those of narcotine, but sparingly soluble in water, readily soluble in the cold 
in alcohol and ether. It melts when heated, and decomposes at a high tem- 
perature. With dilute acids it forms crystallizable compounds, and when 
isolated and in solution has a powerful alkaline reaction. The composition 
of thebaine is C 38 H 21 N0 6 . 

A series of other bases, pseudo-morphine, nareeine, meconine, papaverine, 
opianine, and porphyroxine, are also, at least occasionally, contained in opium; 
they are of small importance, and comparatively little is known respecting 
them. 

Meconic acid is obtained from the impure meconate of lead, as already 
mentioned. The solution is evaporated in the vacuum of the air-pump. A 
more advantageous method is to decompose the impure meconate of lime, 
obtained in Dr. Gregory's morphine-process, by warm dilute hydrochloric 
acid; to separate the crystals of acid meconate of lime, which form on 
cooling, and to repeat this Operation until the whole of the base has been 
removed, which may be known by the acid being entirely combustible, with- 
out residue, when heated in the flame of a spirit-lamp upon platinum foil. 
It is with the greatest difficulty obtained free from colour. 

Meconic acid crystallizes in little colourless, pearly scales, which dissolve 
in 4 parts of hot water. It has an acid taste and reaction, forms soluble 
compounds with the alkalis, and insoluble salts with lime, baryta, and the 
oxides of lead and silver. The most remarkable feature in this substance is 
its property of striking a deep blood-red colour with a salt of the sesqui- 
oxide of iron, exactly resembling that developed, under similar circum- 
stances, by a sulphocyanide. The meconate of iron may, however, be dis- 
tinguished from the latter compound, as Mr. Everitt has shown, by an addi- 
tion of corrosive sublimate, which bleaches the sulphocyanide, but lias little 
effect upon the meconate. This is a point of considerable practical impor- 
tance, as in medico-legal inquiries, in which evidence of the presence of 
opium is sought for in complex organic mixtures, the detection of meconic 
*oid is usually the object of the chemist; and since traces of alkaline sul- 



VEGETO-ALKALIS. 447 

phocyanide are to be found in the saliva, it becomes very desiraole to remove 
that source of error and ambiguity. 

Crystallized meconic acid contains C 14 HO n ,3HO-|-6fIO. 

"When a solution of meconic acid in water, or, still better, in a mineral 
acid, is boiled, or when the dry acid is exposed in a retort to a temperature 
of 400° (204°-5C), it is decomposed, yielding a new bibasic acid, the comenic, 
containing C 12 H 2 8 ,2HO, which much resembles in properties meconic acid. 
Water and carbonic acid are at the same time extricated. At a higher tem- 
perature comenic acid itself is resolved into a second new acid, the pyrome- 
eonic, which sublimes, and afterwards condenses in brilliant colourless plates. 
It is monobasic, and contains C 10 H 3 O 5 ,HO. The salts of meconic acid and 
comenic acid, together with several derivatives of these substances, have 
been lately studied by Mr. How, 1 but our space will not permit us to describe 
these compounds. 

An acid much resembling the meconic has been extracted from the Cheli- 
donium mojas ; it is combined with lime, and associated with malic and fu- 
maric acids. Chelidonic acid is bibasic, forming three classes of salts, and 
a pyro-acid with evolution of water and carbonic acid when exposed to a high 
tempei^ature. It crystallizes in slender colourless needles of considerable 
solubility, containing C 14 H 2 O 10 ,2HO-f-3HO. 

Cinchonine and quinine. — It is to these vegeto-alkalis that the valuable 
medicinal properties of the Peruvian barks are due. They are associated in the 
bark with sulphuric acid, and with a special acid, not found elsewhere, called 
the kinic. Cinchonine is contained in largest quantity in the pale bark, or 
Cinchona condaminea ; quinine in the yellow bark, or Cinchona cordifolia ; the 
Cinchona oblongifolia contains both. 

The simplest, but not the most economical, method of preparing these 
substances, is to add a slight excess of hydrate of lime to a strong decoction 
of the ground bark, in acidulated water; to wash the precipitate which 
ensues, and boil it in alcohol. The solution, filtered while hot, deposits the 
vegeto-alkali on cooling. When both bases are present, they may be sepa- 
rated by converting them into sulphates ; the salt of quinine is the least 
soluble of the two, and crystallizes first. 

Pure cinchonine or cinchonia, crystallizes in small, but beautifully bril- 
liant, transparent four-sided prisms. It is but very feebly soluble in water, 
dissolves readily in boiling alcohol, and has but little taste, although 
its salts are excessively bitter. It is a powerful base, neutralizing acids 
completely, and forming a series of crystallizable salts. 

Quinine, or quina, much resembles cinchonine ; it does not crystallize so 
well, however, and is much more soluble in water ; its taste is intensely 
bitter. 

Cinchonine is composed of C 20 H 12 NO, and 

Quinine of C 20 H ]2 NO 2 . 2 

Sulphate of quinine is manufactured on a very large scale for medicinal 
use ; it crystallizes in small white needles, which give a neutral solution. 
Nevertheless, this substance is a basic salt, and contains 2C 20 H ]2 NO 2 .SO 3 -f- 
8HO. The solubility of this compound is much increased by the addition of 
a little sulphuric acid, whereby the neutral salt C 20 H 12 NO 2 ,SO 3 -|-8HO is 
formed. A very interesting compound has been lately produced by Dr. 

1 Chem. Sec. Quar. Jour. Vol. IY. page 363. 

3 Some doubts are still hanging over the composition of cinchonine and quinine. Accord 
ing to M. Lavrcnt these substances contain respectively CESU24N2O4. and GgHsiNaO-a. If these 
formulas be adopted the basic sulphate of commerce would become a neutral, the neutr-U 
«n acid-salt. 

Commercial sulphate C38n 2 4No02S0 3 -i-8HO 

Soluble sulphate C38ll 2 iN2O 3 ,S03+H0,S0 3 -f 15EO. 



448 VEGETO-AL KALIS. 

Hcrapath, by the action of iodine upon the sulphate of quinine. It is a 
crystalline substance of a brilliant emerald colour, which appears to consist 
of 1 eq. of the sulphate of quinine, and 1 eq. of iodine. This remarkable 
compound possesses the optical properties of the mineral tourmaline. (See 
page 75.) 

Quinidine. — In manufacturing sulphate of quinine, a new base has been 
lately obtained, which differs from quinine in some of its physical proper- 
ties, but is said to have the same composition as quinine. It has been 
described under the name of quinidine, and appears to have the same medi- 
cinal properties as quinine. This substance is not yet sufficiently ex- 
amined. 1 

Chinoidine, quinoidine, or amorphous quinine, is contained in the refuse, or 
mother-liquors of the quinine-manufacture. In its purest state it forms a 
yellow or brown resin-like mass, insoluble in water, freely soluble in alcohol 
and ether. It is easily soluble also in dilute acids, and is thence precipitated 
by ammonia. Quinoidine possesses powerful febrifuge properties, and is 
identical in composition with quinine. It evidently bears to quinine the same 
relation that uncrystallizable syrup does to ordinary sugar, being produced 
from quinine by the heat employed in the preparation. 3 

From Cusco, or Arica-bark, and likewise from the Cinchona ovata, or while 
quinquina of Condamine, a substance denominated aricine or cinchovaiine has 
been extracted; it closely resembles cinchonine, and contains C 20 H ]2 NO 3 i. e. 
1 eq. of oxygen more than quinine, and 2 eq. more than cinchonine. 

This substance is useless in medicine. 

Kinic acid. — Kinate of lime is found in the solution from which the bark- 
alkalis have been separated by hydrate of lime, and is easily obtained by 
evaporation, and purified by animal charcoal. From the lime-salt the acid 
can be extracted by decomposing it by diluted sulphuric acid. The clear 
solution evaporated to a syrupy consistence deposits large, distinct crystals, 
which resemble those of tartaric acid. It is soluble in 2 parts of water, 
and contains Cj 4 H 1 jOi 1 ,HO. 

When kinic acid is heated with a mixture of sulphuric acid and binoxide 
of manganese, it furnishes a very volatile substance termed kinone, the 
vapour of which is exceedingly irritating to the eyes. This new body forms 
crystals both by sublimation and by solution in boiling water ; it melts with 
gentle heat, and crystallizes on cooling, colours the skin permanently brown, 
and contains C 12 H 4 4 . 

By destructive distillation, kinic acid yields numerous and interesting pro- 
ducts, which have been studied by M. Wohler, as benzoic acid, carbolic acid, 
hydride of salicyl, benzol, a tarry substance not examined, and a new body, 
colourless hydrokinone, which possesses very curious relations with the kinone 
above described. It forms colourless six-sided prismatic crystals ; is neu- 
tral, destitute of taste and odour, fusible, and easily soluble both in water 

1 Quina is very soluble in alcohol and ether; its sulphate requires 57 parts of absolute 
and 63 of alcohol of 90 per cent, for solution ; of water 205 parts of cold and 24 of boiling 
are required. The oxalate is completely insoluble in water. 

Quinidine differs in separating from its solution in alcohol in crystals, in its inferior solu- 
bility in alcohol and ether, and the greater solubility of its sulphate in water. It dissolves 
in 140 to 150 parts of ether, 45 of absolute and 105 of alcohol of 90 per cent. Its sulphate 
is soluble in 32 parts of absolute and 7 parts of alcohol of 90 per cent., in 73 parts of cold 
and less than 5 of boiling: water, according to Howard (130 of e2°-6 fl7°C) and 16 of boiling 
Mater.— Leers). The oxalate is very soluble in cold and more freely in boiling water, from 
which crystals are deposited on cooling. 

Quinidine contains Ci 8 HuNO.— 11. B. 

a Amorphous quinine is a mixture of quina, cinchonia. and a resin. Quina may be ob- 
tained from it by dissolving in alcohol, precipitating by protoehloride of tin. filtering, and 
adding ammonia to the clear liquor. The precipitate well washed and dried, and a second 
time treated with protoehloride of tin and ammonia, yields to alcohol pure quina, which 
crystallizes on evaporating the alcohol.— R. B. 



VEGETO-ALKALIS. 449 

and alcohol. With care it may be sublimed unchanged. It contains 
C M H e O, 

Colourless hydrokinone can be easily and directly produced from kinone 
by the assimilation of hydrogen, as by addition of hydriodic acid to a solu- 
tion of the latter, when iodine is set free, or by sulphurous acid, or tellu- 
retted hydrogen. 

An intermediate product of reduction is green hydrokinone. This is ob- 
tained by the incomplete action of sulphurous acid upon kinone, or by the 
action of sesquichloi"ide of iron, chlorine, nitrate of silver, or chromic acid 
upon colourless hydrokinone ; or by mixing together solutions of kinone and 
colourless hydrokinone. " It forms slender green crystals of the colour of the 
wing-case of the rose-beetle, and of the greatest brilliancy and beauty. It 
is fusible, has but little odour, and dissolves freely in boiling water, crys- 
tallizing out on cooling. This substance contains C ]2 H 5 G 4 . 

If kinic acid be submitted to distillation with an ordinary chlorine-mix- 
ture, an acid liquid and a crystalline sublimate are formed. The former is 
a solution of formic acid, the latter a mixture of 4 chlorinetted compounds, 
which are chlorokinone C 12 (H 3 C1)0 4 , bichlorokinone Ci 2 (H 2 C] 2 )0 4 , trichloro- 
kinone C 12 (HC1 3 )0 4 and tetrachlorokinone C ]2 C1 4 4 . They are all yellow 
crystalline substances, which can be separated only with great difficulty. 
Like kinone itself, they possess the faculty of combining with 1 or 2 eq. of 
hydrogen, producing 2 series of substances analogous to green and colour- 
less hydrokinone. Tetrachlorokinone, better known by the name chloranile, 
likewise occurs among the products of decomposition of indigo. 

Other products were obtained by the action of sulphuretted hydrogen and 
strong hydrochloric acid upon kinone, which possess less interest than the 
preceding. 

Strychnine and brucine, also called strychnia and brucia, are contained 
in Nux vomica, in St. Ignatius' bean, and in fake Angustura bark; they are 
associated with a peculiar acid, called the igasuric. Nux vomica seeds are 
boiled in dilute sulphuric acid until they become soft ; they are then 
crushed, and the expressed liquid mixed with excess of hydrate of lime, 
which throws down the alkalis. The precipitate is boiled in spirit of wine 
of sp. gr. 0-850, and filtered hot. Strychnine and brucine are deposited 
together in a coloured and impure state, and may be separated by cold 
alcohol, in which the latter dissolves readily. 

Pure strychnine crystallizes under favourable circumstances in small, but 
exceedingly brilliant octahedral crystals, which are transparent and colour- 
less. It has a very bitter, somewhat metallic taste (1 part in 1,000,000 parts 
of water is still perceptible), is slightly soluble in water, and is fearfully 
poisonous. It dissolves in hot, and somewhat dilute spirit, but neither in 
absolute alcohol, ether, nor in solution of caustic alkali. This alkaloid may 
be readily identified by moistening a crystal with concentrated sulphuric 
acid, and adding to the liquid a crystal of bichromate of potassa, when a 
deep violet tint is produced, which disappears after some time. Strychnine 
forms with acids a series of well-defined salts, lately examined by Messrs. 
Nicholson and Abel, who established for strychnine the formula C 42 U 22 1 S 2 4 

Brucine is easily distinguished from the preceding substance, which it 
much resembles in many respects, by its ready solubility in alcohol, both 
hydrate and absolute. It dissolves also in about 500 parts of hot water. 
The salts of brucine are, for the most part, crystallizable. 

Brucine contains C 46 H 26 N 2 8 . 

Veratrixe (or veratria) is obtained from the seeds of Veratrum sabadilla. 
In its purest state it is a white, or yellowish-white powder, which has a sharp 
burning taste, and is very poisonous. It is remarkable for occasioning violent 
sneezing. It is insoluble in water, but dissolves in hot alcohol, in ether, and 



450 VEGETO-AL KALIS. 

in acids ; the solution has an alkaline reaction. Veratrine contains nitrogen, 
but its composition is yet doubtful. 1 

A substance called colchicine, extracted from the Colchicum autumnale, and 
formerly confounded with veratrine, is now considered distinct ; its history 
is yet imperfect. 

Conine (conictne, or conia), nicotine, and sparteine, differ from the 
other vegetable bases in physical characters ; they are volatile oily liquids. 
The first is extracted from hemlock, the second from tobacco, and the third 
from broom (spartium scoparium). They agree in most of their characters, 
having high boiling-points, very poisonous properties,«strong alkaline reaction, 
and the power of forming with acids crystallizable salts. The formula of 
nicotine is C 10 H 7 N ; that of conine, C, 6 H 15 N, and that of sparteine C ]5 H 13 N. 
A series of substances as it appears closely related to nicotine will be men- 
tioned among the artificial organic bases. 

The basic substance contained in the juice of animal flesh, kreatinine, will 
be found described among the components of the animal body. 

Harmaline. — This compound is extracted by dilute acetic acid from the 
seeds of the Peganum harmala, a plant which grows abundantly in the Steppes 
of Southern Russia, and the seeds of which are used in dyeing. When pure, 
it forms yellowish prismatic crystals, soluble in alcohol and dilute acids, but 
scarcely forming crystallizable salts. By oxidation it gives rise to another 
compound, harmine, which itself possesses basic properties. The seeds are 

and harmine 

Caffeine, or theine. — This remarkable substance occurs in four articles 
of domestic life, infusions of which are used as a beverage over the greater 
part of the known world, namely, tea and coffee, and the leaves of Guarana 
officinalis, or Paullinia sorbilis, and in those of Ilex paraguayensis ; it will pro- 
bably be found in other plants. A decoction of common tea, or of raw coffee- 
berries, previously crushed, is mixed with excess of solution of basic acetate 
of lead. The solution, filtered from the copious yellow or greenish precipi- 
tate, is treated with sulphuretted hydrogen to remove the lead, filtered, 
evaporated to a small bulk, and neutralized by ammonia. The caffeine 
crystallizes out on cooling, and is easily purified by animal charcoal. It 
forms tufts of delicate, white, silky needles, which have a bitter taste, melt 
when heated with loss of water, and sublime without decomposition. It is 
soluble in about 100 parts of cold water, and much more easily at a boiling- 
heat, or if an acid be present. Alcohol also dissolves it, but not easily. 
Caffeine contains C, 6 H 10 N 2 O 4 . The basic properties are feeble. The salts 
with hydrochloric and sulphuric acid are obtained only with difficulty. It 
forms, however, splendid double-salts with bichloride of platinum and ter- 
chloride of gold. The products of oxidation of caffeine, which have been 
lately studied by Rochleder, are of considerable interest, inasmuch as both 
their composition and their properties establish a close connection of these 
products with the derivatives of uric acid. Under the influence of chlorine, 
caffeine yields a substance of feebly acid properties, which contains C )2 H 7 N 2 8 . 
This compound, which has received the name amalic acid, is homologous to 
alloxantin. When treated with oxidizing agents, it yields cholestrophanc, 
C 10 HgN 2 O 6 , the parabanic acid of the uric acid-series. The murexide of the 
caffeine-series lastly is formed by the treatment of amalic acid with ammonia, 

1 According to Courbe, it contains Ciun^NOfl. Several of these bases may he distinguished 
hy nitric acid. Brucia hecomes bright red, which is soon changed to purple by chloride of 
tin. Pure strychnine becomes yellow. Yeratria, orange red, soon changing to yellow. 
Morphia, hright red, changed to yellow by chloride of tin. — II. B. 



VEGETO- ALKALIS. 45 1 

exactly as the murexide par excellence is formed by the action of ammonia 
upon alloxantin. The new murexide imitates its prototype not only in com- 
position, but likewise in the green metallic lustre of its crystals, and the 
deep crimson colour of its solutions. The homology of these compounds 
with the members of the uric acid-series is well illustrated by a comparison 
of their formulae — 

Alloxantin C 8 H 3 N 2 8 +2C 2 H 2 =C 1 ,H 7 N 2 8 Amalic acid 
Parabanic acid C 6 H 2 N 2 6 -j- 2C 2 H 2 ==C 10 H 6 N 2 6 Cholestrophane 
Murexide Cj 2 H 6 N 5 8 -f-3C 2 H 2 ==C, 8 H 12 N 5 8 Caffeine-murexide 

Theobromine. — The seeds of the Theobroma cacao, or cacao-nuts, from 
which chocolate is prepared, contain a crystallizable principle to which the 
preceding name is given. It is extracted in the same manner as caffeine, 
and forms a white, crystalline powder, which is much less soluble than the 
last-named substance. It contains, according to Glasson, C 14 H 8 N 4 4 . Ac- 
cordingly it is homologous to caffeine. The products obtained from theo- 
bromine by oxidation appear to be likewise homologous with terms ef the 
uric acid-series. 

Berberine. — A substance crystallizing in fine yellow needles, slightly 
soluble in water, extracted from the root of the Berberis vulgaris. It has 
feeble basic properties, and contains C 42 H ]8 N0 9 . This must not be confounded 
with beeberine, an uncrystallizable basic substance, from the bark of the 
green-heart timber of Guiana, which has the composition C 38 H 21 N0 6 . It forms 
with acids uncrystallizable salts. 

Piperixe. — A colourless, or slightly yellow crystallizable principle, ex- 
tracted from pepper by the aid of alcohol. It is insoluble in water. Formula 
C 34 rI lg N0 6 . Piperine readily dissolves in acid ; definite compounds however 
are obtained only with difficulty. 

There are very many other bodies, more or less perfectly known, having 
to a certain extent the properties of salt-bases ; the following statement of 
the names and mode of occurrence of a few of these must suffice. 

Hyoscy amine (Dalurine). — A white, crystallizable substance, from Hyos- 
cyamus niger ; it occurs likewise in Datura stramonium, formula C^H^NOg. 

Atropine. — Colourless needles, from Atropa belladonna, formula C 34 H 23 N0 6 . x 

Solanine. — A pearly, crystalline substance, from various solanaceous plants. 

Aconitine. — A glassy, transparent mass, from Aconitum napellus : formula 

Delphinine. — A yellowish, fusible substance, from the seeds of Delphinium 
staphisagria. 

Emetine. — A white and nearly tasteless powder from ipecacuanha root. 
Curarine. — The arrow-poison of Central America. 



There exists an extensive series of neutral, usually bitter, and sometimes 
poisonous vegetable principles, which are allied in some measure to the 
vegeto-alkalis. Some of these are destitute of nitrogen. Two of the num- 
ber, salicin and phloridzan, have been already described (see pages 403 and 
406) ; the most important of the remainder are the following : — 

Gentiaxin. — The bitter principle of the gentian-root, extracted by ether. 

* Crystallizes from a saturated hot aqueous solution in silky tufts; colourless, inodorous, 
very bitter, soluble in 25 parts of ether, 2000 parts cold and 54 of hot water. lias a strong 
alkaline reaction, and forms crystallizable salts. It is probably identical with daturine — 
R. B. 

a Crystallizes from an alcoholic solution in small grains; soluble readily in alcohol a:id 
ether, and also in 100 parts cold and 50 boiling water; has a sharp, bitter taste, and alkaline 
reaction. Its salts are not crystallizable.— R. B. 



452 VEGETO-AL KALIS. 

It crystallizes in golden-yellow needles, is sparingly soluble in cold water, 
more soluble in hot water, and freely dissolved by alcohol and ether. Its 
composition is C 14 H 5 5 . 

Populin. — This substance closely resembles salicin in appearance and solu- 
bility, but has a penetrating sweet taste ; it is found accompanying salicin in 
the bark and leaves of the aspen. According to recent researches of Piria, 
populin contains C 40 H 22 O l6 -f-4HO. It is a conjugate compound of salicin and 
benzoic acid. 

^40^26^20 " ^14^6^4 + C 26 H 1R O u -'-2HO 

Crystall. Populin. Benzoic acid. Salicin. 

By the action, of reagents it is converted into benzoic acid, and the products 
of decomposition of salicin. With dilute acid it yields benzoic acid, grape- 
sugar, and saliretin ; when treated with a mixture of sulphuric acid and 
bichromate of potassa, it furnishes a considerable quantity of hydride of 
salicyl. 

Daphnin. — Extracted from the bark of the Daphne mezereum; it forms 
colourless, radiated needles, freely soluble in hot water, alcohol and ether. 

Hesperidin. — A white, silky, tasteless substance, obtained from the spongy 
part of oranges and lemons. It dissolves in 60 parts of hot water ; also in 
alcohol and ether. 

Elaterin. — The active principi^ of Momordica elaterium. It is a white, 
silky, crystalline powder, insoluble in water. It has a bitter taste, and ex- 
cessively violent purgative properties. Alcohol, ether, and oils dissolve it. 
Exposed to heat, it melts and afterwards volatilizes. It contains C 20 H 14 O 5 . 

Antiarin.— The poisonous principle of the Upas antiar. It forms small, 
pearly crystals, soluble in 27 parts of boiling water, and also in alcohol, but 
scarcely so in ether; it cannot be sublimed without decomposition. Intro- 
duced into a wound, it rapidly brings on vomiting, convulsions, and death. 
Antiarin contains C 14 H 10 O 5 . 

Picrotoxin. — It is to this substance that Cocculus indieus owes its active 
properties. Picrotoxin forms small, colourless, stellated needles, of inex 
pressibly bitter taste, which dissolve in 25 parts of boiling ale x hol. It con- 
tains C 10 H 6 O 4 . 

Asparagin. — This, and the two following, are azotized bodies. Asparagin 
is found in the root of the marsh-mallow, in asparagus sprouts, and in several 
other plants. The mallow-roots are chopped small, and macerated in the cold 
with milk of lime : the filtered liquid is precipitated by carbonate of ammonia, 
and the clear solution evaporated in a water-bath to a syrupy state. The 
impure asparagin, which separates after a few days, is purified by re-crys- 
tallization. Asparagin forms brilliant, transparent, colourless crystals, 
which have a faint cooling taste, and are freely soluble in water, especially 
when hot. When dissolved in a saccharine liquid, which is afterwards made 
to ferment, when heated with water under pressure in a close vessel, or when 
boiled with an acid or an alkali, it is converted into ammonia and a new acid, 
the asparlic. Asparagin contains C 8 H 8 N 2 6 , and aspartic acid C 8 H 7 N0 8 . The 
remarkable relation in which these substances stand to malic acid has been 
already noticed under the head of malic acid (see p. 415). 

Santonin. — This substance is the crystalline principle of several varieties 
of Artemisia. In order to obtain it, the seeds are crushed, and digested 
with lime and spirit of wine, when a yellow liquid is obtained, from which 
the alcohol is separated by distillation. The residuary liquid is saturated 
with acetic acid, when the santonin crystallizes. This substance is easily 
Bolubie in water and alcohol, and contains C 30 H ls O 6 . Santonin possesses the 
character of a weak acid. 



ORGANIC BASES OF ARTIFICIAL ORIGIN. 453 



ORGANIC BASES OF ARTIFICIAL ORIGIN. 

The constitution of the alkaloids, which occur ready formed in nature, 
is not yet clearly understood. The fact that all these substances contain 
nitrogen, — the alkaline reaction, which the greater part of them exhibits 
•with vegetable colours, and especially their faculty of combining with acids 
to crystallizable salts, establish an obvious relation between the alkaloids 
and ammonia. This has never been doubted, and the views of chemists 
have been divided only as to the form of this relation. At a certain time 
Berzelius assumed that all the alkaloids contained ammonia ready formed, 
and that their basic properties were due to this ammonia. According to 
this view the formulae of quinine and morphine would be — 

Quinine C 20 H ]2 NO 2 =C 2p H 9 2 ,NH 3 

Morphine.... C 34 H 19 N0 6 = C 34 H 16 6 ,NH 3 . 

This view, in the general form in which it was proposed, is certainly inad- 
missible. It is supported by very scanty experimental evidence, and was 
never universally adopted. There may be some alkaloids so constituted as 
represented by the theory of Berzelius. There are, however, a great many, 
the constitution of which is obviously different. Several of these substances 
have been lately the subject of extensive and careful inquiries ; but these 
researches, although they have established their formulae and increased our 
knowledge regarding their salts, have as yet elicited but few facts which 
promise to afford a clearer insight into the nature of these bodies. 

On the other hand, the labours of the last ten years have brought to light 
a very numerous group of substances perfectly analogous to the alkaloids 
which are found in plants, but produced by artificial processes in the labo- 
ratory. These bodies, which are termed artificial alkaloids or artificial or- 
ganic bases, are mostly volatile. Their constitution is much simpler than 
that of the native bases. The very processes which give rise to their forma- 
tion often permit a very clear insight into the mode in which the elements 
are grouped, and in the relation existing between these substances and am- 
monia. 

In a former section of this volume (page 232), it has been stated that the 
majority of chemists incline to assume in the ammoniacal salts the existence 
of a compound metal ammonium NH 4 , 

Chloride of ammonium, NH 4 C1 
Sulphate of ammonia, NH 4 0,S0 3 . 

Now, recent researches have shown, that in these salts, 1, 2, 3, or even the 
4 eq. of hydrogen may be replaced by compound radicals, containing vari- 
able proportions of carbon and hydrogen, without any change in their fun- 
damental properties. It is evident that we obtain in this manner, in addi- 
tion to the ammoniacal salts, four new series of compounds very closely 
allied to the former. Let A B C D represent a series of such radicals capable 
of replacing hydrogen, then the following series of salts may be brmedi - 



Ammonia-salts N^ £ > CI N^ £ >0,S0 3 . 

First group of compound 



ammonia-salts 




M h > Cl N S H >°> S0 3 




454 ORGANIC BASES OP ARTIFICIAL ORIGIN. 



Second group of com- 
pound ammonia-salts 



Third group of compound 
ammonia-salts 



Fourth group of com- „ J B ( n nJ B VOSO 

pound ammonia-salts iN U f L1 iN \ C r u > toU 3- 

It need scarcely be mentioned that it is by no means necessary that the 
several hydrogen-equivaleuts in ammonia should be replaced by different 
radicals, as assumed in the preceding table. Substances of the formulae — 



N- 



are even more easily prepared and more frequently met with. 

This synopsis shows that the number of salts capable of being derived from 
the ordinary ammoniacal salts, must be very considerable. Even now a very 
extensive series has been prepared, although the number of radicals at our 
disposal at present is still comparatively limited. 

It has been mentioned that all attempts at isolating both ammonium and 
its oxides have hitherto failed (see page 232). On treating chloride of am- 
monium or sulphate of ammonia with mineral oxides, such as potassa, lime, 
and baryta, decomposition ensues, chloride of potassium or sulphate of po- 
tassa, &c, is formed, and the separated oxide of ammonium splits into 
ammonia-gas and watei% NH 4 0=NH 3 -|-HO (see page 162). 

The compound ammonia-salts are likewise decomposed by mineral oxides. 
With the three first classes the change is perfectly analogous to that of am- 
moniacal salts, the separated oxide is decomposed into water and a volatile 
base, the properties of which, according to the nature of the replacing radi- 
cals, are more or less closely approximated to those of ammonia itself. We 
arrive in this manner at three groups of organic bases, differing from one 
another by the amount of hydrogen which is replaced ; they have been dis- 
tinguished by the terms amidogen-, imidogen-, and nitrile-bases. 

ii r a 



A \ 
H 


>C1 


..... N^ 


I A 
1 A 


H 






u 



N \ H N \ II N 

H I H 



\ B N^ B 

Ih [c 



Ammonia. Amidogen- Imidogen- Nitrile-bases. 

bases. bases. 

The last group of ammoniacal salts, in which the 4 eq. of hydrogen are 
replaced by radicals, differ in their deportment from the former classes. 
These salts are not decomposed by potassa, but yield, by appropriate treat- 
ment, a series of substances of a very powerfully alkaline character, which 
are expressed by the general formula; : — 

nJ B VO, HO, 



ORGANIC BASES OF ARTIFICIAL ORIGIN. 455 

are evidently analogous to hydrated oxide of ammonium ; from which they 
differ, however, in a remarkable manner, by their powerful stability. 

These general statements will become more intelligible if we elucidate them 
by the description of several individual substances ; the limits of this work 
compel us, however, to confine ourselves to the more important members of 
this already very numerous group, which is moreover daily increasing. 

It may at once be stated that by far the greater number of these compounds 
are derived from the alcohols or substances analogous to them, and that the 
radicals which in the preceding sketch have been designated by the letters 
A, B, C, and D, are chiefly the hydrocarbons previously described under the 
names ethyl, methyl, and amyl. 

BASES OF THE ETHYL-SERIES. 

Ethylaxjne, Ethyl-ammonia, C 4 If 7 N — (H 2 ,C 4 H 5 ) = N(H 2 Ae). — On digest- 
ing bromide or iodide of ethyl (see page 353) with an alcoholic solution of 
ammonia, the alkaline reaction of the ammonia gradually disappears. On 
evaporating the solution on the water-bath a white crystalline mass is 
obtained, which consists chiefly of bromide of ethyl-ammonium, AeI-J-NH 3 
= N(H 3 Ae)I. On distilling this salt in a retort provided with a good con- 
denser, with caustic lime, the ethylamine is liberated and distils over, 

NH 2 AeI+K0==N(H 2 Ae)-fH0-f-KL 

Another method of preparing this compound, and indeed the method by 
which this remarkable substance Avas first obtained by M. Wurtz, consists in 
submitting cyanate of ethyl to the action of hydrate of potassa. In describ- 
ing cyanic acid (see page 426), the interesting change has been mentioned, 
which this substance undergoes when treated with boiling solution of potassa. 
In this case cyanic acid splits into 2 eq. of carbonic acid and 1 eq. of am- 
monia ; cyanate of ethyl (see page 428) suffers a perfectly analogous decom- 
position, and instead of ammonia we obtain ethylamine. 

C 2 NO,HO-f2(KO,HO) = 2(KO,C0 2 )-fNH 3 

Hydrated 
cyanic acid. 

C 2 NO,AeO + 2(KO,HO) = 2(KO,C0 2 )-fN(H 2 Ae) 

Cyanate of Ethylamine. 

ethyl. 

Cyanur.ete of ethyl, isomeric with the cyanate, likewise furnishes ethylamine. 

Ethylamine is a very mobile liquid of 0-6964 sp. gr., at 46°-4 (8°C), which 
boils at 64°-4 (18°C). The sp. gr. of the vapour is 1-57. It has a most 
powerfully ammoniacal odour, and restores the blue colour to reddened 
litmus paper. It produces white clouds, with hydrochloric acid, and is 
absorbed by water with great avidity. With the acids it forms a series of 
neutral crystallizable salts perfectly analogous to those of ammonium. 

This substance imitates, moreover, in a remarkable manner, the deport- 
ment of ammonia with metallic salts. It precipitates the salts of magnesia, 
alumina, iron, manganese, bismuth, chromium, uranium, tin, lead, and mer- 
cury. Zinc-salts yield a white precipitate which is soluble in excess. Like 
ammonia, ethylamine dissolves chloride of silver, and yields with copper- 
salts a blue precipitate, which is soluble in an excess of ethylamine. On 
adding ethylamine to oxalic ether, a white precipitate of ethyl-oxamide. 
N(HAe),C 2 2 , is produced ; even a compound analogous to oxamic acid (see 
page 343) has been obtained. Ethylamine may, however, be readily distin- 



456 ORGANIC BASES OF ARTIFICIAL ORIGIN. 

guished from ammonia ; its vapour is inflammable, and it produces, with 
bichloride of platinum, a salt N(H 3 Ae)Cl,PtCl 2 , crystallizing in golden scales, 
■which are rather soluble in -water. If ethylamine is treated with chlorine, 
it furnishes chloride of ethyl-ammonium and a yellow liquid of a penetrating 
odour exciting tears, which contains NCl 2 A.e. This substance is bichlorethyl- 
amine. When treated with potassa it is converted into ammonia, acetate of 
potassa, and chloride of potassium, NCl 2 ,C 4 H 6 ^3KO-{-HO=KO,C 4 H 3 3 4- 
NH 3 +2KC1. 

Ethylamine-urea. On passing into a solution of ethylamine, the vapour of 
hydrated cyanic acid, the liquid becomes hot, and deposits after evaporation, 
fine crystals of ethylamine-urea, C 4 H 7 N-f C 2 NO,HO==C 6 H 8 N 2 2 =C 2 (H 3 ,C 4 
H 5 )N 2 2 =C 2 (H 3 Ae)N 2 2 . This substance, which may be received as ordinary 
urea (see page 436), in which 1 eq. of hydrogen is replaced by ethyl, may 
be prepared also by treating cyanic ether with ammonia, C 4 H 5 0,C 2 NO-f-NH 3 
— C 6 H 8 N 2 2 . Ethylamine urea is very soluble in water and alcohol ; the 
concentrated aqueous solution, unlike that of ordinary urea, yields no pre- 
cipitate with nitric acid ; but on gently evaporating the mixture, a very 
soluble crystalline nitrate of ethylamine-urea is obtained. Boiled with po- 
tassa, this substance yields a mixture of equal equivalents of ammonia and 
ethylamine, C 2 (H 3 Ae)N 2 2 -f 2(KO,HO)=2(KO,C0 2 ) -f NH 3 -f N(H 2 Ae). 

Biethylamine, Biethyham,monia, C 8 H u N = NH,2C 4 H 5 =N(HAe 2 ). — A mix- 
ture of solution of ethylamine and bromide of ethyl, heated in a sealed tube 
for several hours, solidifies to a crystalline mass of bromide of bietbyl- 
ammonium, N(H 2 Ae)-j- AeBr=N(H 2 Ae 2 )Br. The bromide, when distilled 
with potassa, furnishes a colourless liquid, still very alkaline, and soluble in 
water, but less so than ethylamine. This compound boils at 133° (55°C). 
It forms beautifully crystallizable salts with acids. A solution of chloride 
of biethyl-ammonium furnishes with bichloride of platinum, a very soluble 
double salt, N(H 2 Ae 2 )Cl,PtCl 2 , crystallizing in orange-red grains, very diffe- 
rent from the orange-yellow leaves of the corresponding ethyl-ammonium- 
salts. 

Biethylamine-urea. Biethylamine probably behaves with cyanic acid like 
ammonia and ethylamine, giving rise to biethylamine-urea. This substance 
has been produced by the action of cyanic ether upon ethylamine, C 4 H 5 0, 
C 2 NO-f C 4 H 7 N = C 10 H 12 N 2 O 2= C 2 (H 2 2C 4 H 5 )N 2 O 2= C 2 (H 2 Ae 2 )N 2 O 2 . Biethyla- 
mine-urea is very crj^stallizable, and readily forms a crystalline nitrate. 
Boilea with potassa, biethylamine-urea yields pure ethylamine, C 2 (H 2 Ae 2 )N 2 
2 +2(KO,HO) = 2(KO,C0 2 )-J-2N(H 2 Ae). 

Triethylamine, Triethyl-ammonia, C 12 H 15 N=N3C 4 H 5 = NAe 3 . — The for- 
mation of this body is perfectly analogous to those of ethylamine and bie- 
thylamine. On heating for a short time a mixture of biethylamine with 
bromide of ethyl in a sealed glass tube, a beautiful fibrous mass of bromide 
of triethyl-ammonium is obtained, from which the triethylamine is sepa- 
rated by potassa. Ti^iethylamine is a colourless, powerfully alkaline liquid, 
boiling at 195°-8 (91°C). The salts of this base crystallize remarkably well. 
With bichloride of platinum it forms a very soluble double salt, N(HAe 3 ) 
Cl,PtCl 2 , which crystallizes in magnificent large orange-red rhombs. 

Hydrated Oxide of Tetrelhyl- ammonium, C 20 H 2 ,iNO 2 = N4(C 4 H 5 )O,IIO = 
NAe 4 0,HO. — When anhydrous triethylamine is mixed with dry iodide of 
ethyl, a powerful reaction ensues, the mixture enters into ebullition, and so- 
lidifies on cooling to a white crystalline mass of iodide of tetrethyl-ammonium, 
NAe 3 -f- AeI = NAe 4 I. The new iodide is readily soluble in hot water, from 
which it crystallizes on cooling in beautiful crj'stals of considerable size. This 
substance is not decomposed by potassa ; it may be boiled with the alkali for 
hours without yielding a trace of volatile base. The iodine may, however, 
be. readily removed by treating the solution with silver-salts. If in this case 



ORGANIC BASES OF ARTIFICIAL ORIGIN. 457 

sulphate or nitrate of silver be employed, we obtain together with iodide of 
silver, the sulphate or nitrate of oxide of tetrethyl-arnmonium, which crys- 
tallize on evaporation ; on the other hand, if the iodide be treated with freshly 
precipitated protoxide of silver, the oxide of tetrethyl-arnmonium itself is 
separated. On filtering off the silver-precipitate, a clear colourless liquid is 
obtained, which contains the isolated base in solution. It is of a strongly 
alkaline reaction, and has an intensely bitter taste. Solution of oxide of 
tetrethyl-arnmonium has a remarkable analogy to potassa and soda. Like 
the latter substance, it destroys the epidermis and saponifies fatty substances 
with formation of true soaps. With the salts of the metals, this substance 
exhibits exactly the same reactions as potassa. On evaporating a solution 
of the base in vacuo, long slender needles are deposited, which are evidently 
the hydrate of the base, with an additional amount of water of crystallization. 
After some time these needles disappear again, and a semi-sojid mass is left, 
which is the hydrate of oxide tetrethyl-arnmonium. A concentrated solution 
of this substance in water may be boiled without decomposition, but on 
heating the dry substance, it is decomposed into pure triethylamine and 
olefiant gas. 

NAe 4 0,H0 = 2HO+ NAe 3 + C 4 H 4 . 

Oxide of tetrethyl-arnmonium forms neutral-salts with the acids. They 
are mostly very soluble ; several yield beautiful crystals. The platinum 
salt, NAe 4 Cl,PtC! 2 , forms orange-yellow octahedrons, which are of about the 
same solubility as the corresponding bichloride of platinum and potassium. 

Oxide of tetrethyl-arnmonium is obviously perfectly analogous to the 
hitherto hypothetical oxide of ammonium. It is a compound of remarkable 
stability, the existence and properties of which must be regarded as power- 
ful supports of the ammonium-theory. 

EASES OF THE METHYL-SERIES. 

Methylamine, Methylammonia, C 2 H 5 N = N(H 2 ,C 2 H 3 ) = N(H 2 Me). — The 
formation and the method of preparing this compound from the cyanate of 
methyl, is perfectly analogous to those of ethylamine (see page 455) ; how- 
ever, methylamine being a gas at the common temperature, it is necessary 
to cool the receiver by a freezing mixture. The distillate, which is an 
aqueous solution of methylamine, is saturated with hydrochloric acid, and 
evaporated to dryness. The crystalline residue, which is the chloride of 
methyl-ammonium, when distilled with dry lime, yields methylamine gas, 
which, like ammonia gas, has to be collected over mercury. It is distin- 
guished from ammonia, by a slightly fishy odour, and by the facility with 
which it burns. Methylamine is liquefied about 32° (0°C), its sp. gr. 
is 1-08. This substance is the most soluble of all gases, at 53°-6 (12°C) 1 
volume of water absorbs 1040 volumes of gas. It is likewise very readily 
absorbed by charcoal. In its chemical deportment with acids and other 
substances, methylamine resembles in every respect ammonia and ethyl- 
amine. Methylamine appears to be produced in a great number of pro- 
cesses of destruc live distillation; it has been formed by distilling several 
of the natural organic bases, such as codeine, morphine, caffeine, and 
several others, with caustic potassa ; frequently a mixture of several bases 
are produced in this manner. 

Among the numerous derivatives already obtained with this substance, 
methylamine-urea C 2 (H 3 Me)N 2 2 , and bimcthylamine-urea C 2 (H 2 Me 2 )N 2 2 , and 
even a methyl- ethy ■[ amine-urea C 2 (H 2 MeAe)N 2 2 may be quoted. The latter 
substance has been produced by the action of cyanate of ethyl upon methyl- 
amine. Even a series of platinum-bases analogous to those produced by the 
39 



458 ORGANIC BASES OF ARTIFICIAL ORIGIN. 

action of ammonia upon protochloride of platinum (see page 309), have been 
obtained with methylamine. 

Bimethylamine has not yet been prepared in a pure state. 

Trimethylamine, trimethyl-ammonia, C 6 H 9 N = N3C 2 H 3 = NMe 3 . — This 
substance is readily obtained in a state of perfect purity, by submitting 
oxide of tetramethyl-ammonium (see the following compound) to the action 
of heat. It is gaseous at the common temperature, but liquefies at about 
48°-2 (9°C) to a mobile fluid of very powerfully alkaline reaction. Tri- 
methylamine produces with acids very soluble salts. The platinum-salt 
N(HMe 3 )Cl.PtCl 2 , is likewise very soluble and crystallizes in splendid orange- 
red octahedrons. According to Mr. "Winkles, large quantities of trimethyl- 
amine are found in the liquor in which salt herrings are preserved. 

Hydrated oxide op tetramethyl-ammonium, C 8 H 13 N0 2 — N4C 2 rT 3 ,0, 
HO = NMe 4 0,HO. — The corresponding iodide maybe obtained by adding 
iodide of methyl to the preceding compound. Both substances unite with a 
sort of explosion. The same iodide is prepared, however, with less diffi- 
culty, simply by digesting iodide of methyl with an alcoholic solution of am- 
monia. In this reaction, a mixture of the iodides of ammonium, methyl- 
ammonium, bimethyl-ammonium, trimethyl-ammonium, and tetramethyl- 
ammonium is produced. The first and last compound form in largest 
quantity, and may be separated by crystallization, the iodide of tetramethyl- 
ammonium being rather difficultly soluble in water. From the iodide the 
base itself is separated by means of protoxide of silver. The properties 
are similar to those of the corresponding ethyl-compound. It differs, how- 
ever, from oxide of tetrethyl-ammonium in its behaviour when heated 
(see page 457), yielding as it does trimethylamine, and pure methyl-alcohol, 
NMe 4 0,HO = NMe 3 -f MeO,HO. 

BASES OF THE AMYL-SERIES. 

The formation of these bodies being perfectly analogous to that of the 
corresponding terms in the ethyl-series, we refer to the more copious state- 
ment given in page 455, and confine ourselves to a brief observation of their 
principal properties. 

Amylamine, amyl-ammonia, C 10 H l3 N=N(H 2 ,Cj H 11 )=N(H 2 Ayl), colour- 
less liquid of a peculiar penetrating aromatic odour, slightly soluble in 
water, to which it imparts a strongly alkaline reaction. With the acids it 
forms crystalline salts, which have a fatty lustre. Amylamine boils at 
199°-4 (93°C). 

An amy/amine-urea has been prepared. 

Biamylakine, biamyl-ammonia, C 20 H 23 N = :N(H,2C 10 H n )=N(HAy] 2 ), aro- 
matic liquid, less soluble in water, and less alkaline than amylamine. It 
boi.s at about 338° (170°C). 

Triamylamine, triamyl- ammonia, C 30 H 33 N=N3C, H u =NAy] 3 , colourless 
liquid of properties similar to those of the two preceding bases, but boiling 
at 494°-6 (257°C). The salts of triamylamine are very insoluble in water, 
and fuse, when heated, to colourless liquids, floating upon water. 

Hydrated oxide op tetramyl-ammonium, C 40 H 45 NO 2 =N4C 10 H n ,O,HO 
==NAyl, 4 0,H0. — This substance is far less soluble than the corresponding 
bases of the methyl- and ethyl-series. On adding potassa to the aqueous 
solution the compound separates as an oily layer. On evaporating the 
solution in an atmosphere free from carbonic acid, the alkali may be ob- 
tained in splendid crystals of considerable size. When submitted to distilla- 
tion it splits into water, triamylamine, and amylene (see page 390),- NAylO, 
IIO--2IIO + NAyl 3 -f-C 10 H 10 . 



ORGANIC BASES OF ARTIFICIAL ORIGIN. 450 



BASES OF THE PHENYL-SERIES. 

Antline, phenylamine, C ]2 H 7 N = N(H 2 ,C ]2 H 5 ) = N(H 2 Pyl). — Under the 
head of salicylic acid (see page 406, and also page 399), a volatile crystal- 
line substance has been noticed by the name of hydrated oxide of phenyl. 
This substance, of which a fuller description is given in Section IX., imitates 
to a certain extent the deportment of an alcohol, but several very character- 
istic transformations of the alcohols, and especially the conversion into the 
corresponding acid, have not as yet been realized. The organic base, how- 
ever, which is derived from this alcohol in the same manner as methylamine, 
ethylamine, and amylamine, from methyl-, ethyl-, and amyl-alcohol, is known 
under the term aniline, a name given to it on account of its relation to the 
indigo-series. Aniline cannot be produced from phenyl-alcohol by the same 
processes which have furnished the bases of the other alcohols, neither bro- 
mide nor iodide of phenyl having as yet been obtained. However, on heating 
phenyl-alcohol with ammonia in sealed tubes, aniline is produced, PylO,HO 
-j-NH 3 ==2HO-f-N(H 2 Pyl). This process, however, although interesting as 
establishing clearly the relation of aniline and phenyl-alcohol, is not calcu- 
luted to yield large quantities of this substance. Aniline is invariably 
obtained either from indigo or from nitrobenzol. 

Powdered indigo boiled with a highly-concentrated solution of hydrate of 
potassa dissolves with evolution of hydrogen gas to a brownish-red liquid 
containing a peculiar acid, the chrysanilic, which becomes gradually converted 
into another acid, the anthranilic (see page 474). If this matter be trans- 
ferred to a retort and still farther heated, it swells up and disengages ani- 
line, which condenses in the form of oily drops in the neck of the retort and 
in the receiver. Separated from the ammoniacal water by which it is accom- 
panied, and re-distilled, it is obtained nearly colourless. The formation of 
aniline from indigo is represented by the following equation : — 

C 16 H 5 X0 2 -f2(KO,HO)-f2HO=C ]2 H 7 N+4(KO,C0 2 )-f4H. 

Indigo. Aniline. 

In order to prepare aniline from nitrobenzol (see page 399), this substance 
is submitted to a process discovered by Zinin, which has proved a very abun- 
dant source of artificial organic bases. An alcoholic solution of nitro-benzol 
is treated with ammonia and sulphuretted hydrogen, until after some hours a 
precipitate of sulphur takes place. The brown liquid is now saturated again 
with sulphuretted hydrogen, and the process repeated until sulphur is no 
longer separated. The reaction may be remarkably accelerated by occasion- 
ally heating or distilling the mixture. The liquid is then mixed with excess 
of acid, filtered, boiled to expel alcohol and unaltered nitrobenzol, and then 
distilled with excess of caustic potassa. The transformation of nitrobenzo; 
into aniline is represented by the equation : — 

C 12 H 5 N0 4 +6HS=C l2 H 7 N-f4HO-f6S 

Nitrobenzol. Aniline. 

If the aniline be required quite pure, it must be converted into oxalate, the 
salt several times crystallized from alcohol, and again decomposed by hydrate 
of potassa. 

Aniline exists among the products of the distillation of coal, and probably 
of other organic matters ; it is formed in the distillation of anthranilic acid 
(see page 474), and occasionally in other reactions. 

When pure, aniline forms a thin, oily, colourless liquid, of faint vinous 



460 ORGANIC BASES OF ARTIFICIAL ORIGIN. 

odour, and aromatic, burning taste. It is very volatile, but nevertheless has 
a high boiling-point* 359°-6 (182°C). In the air it gradually becomes yellow 
or brown, and acquires a resinous consistence. Its density is 1-028. Water 
dissolves aniline to a certain extent, and also forms with it a kind of hydrate ; 
alcohol and ether are miscible with it in all proportions. It is destitute of 
alkaline reaction to test-paper, but is quite remarkable for the number and 
beauty of the crystallizable compounds it forms with acid'-. Two extraordi- 
nary reactions characterize this body and distinguish it from all others, viz., 
that with chromic acid, and that with solution of hypochlorite of lime. The 
former gives with aniline a deep greenish or bluish-black precipitate, and 
the latter an extremely beautiful violet-coloured compound, the fine tint of 
which is, however, very soon destroyed. 

Substitution-products of aniline. — Under the head of indigo, a product of 
oxidation of this substance will be noticed, to which the name isatin has 
been given (see page 471). When isatin is distilled with an exceedingly con- 
centrated solution of caustic potassa, it is, like indigo, resolved into aniline, 
carbonic acid, and free hydrogen. In like manner, when chlorisatin or 
bichlorisatin, two chloro-substitutes of isatin, are similarly treated, they yield 
products analogous to aniline, but containing one or two equivalents of chlo- 
rine respectively in place of hydrogen. The chloraniline, C 12 (H 6 C1)N, and 
bichlor aniline, C 12 (H 5 C1 2 )N, thus produced, cannot be obtained directly, how- 
ever, from aniline by the action of chlorine, thus differing from ordinary 
substitution-compounds ; but aniline may be reproduced from them by the 
same re-agent, which is capable of reconverting chloracetic acid into ordi- 
nary acetic acid, namely, an amalgam of potassium (see page 375). They are 
the first cases on record of organic bases containing chlorine. 

Chloraniline forms large, colourless octahedrons having exactly the odour 
and taste of aniline, very volatile, and easily fusible ; it distils without de- 
composition at a high temperature, and burns, when strongly heated, with a 
red smoky flame with greenish border. It is heavier than water, indifferent 
to vegetable colours, and, except in being solid at common temperatures, re- 
sembles aniline in the closest manner. It forms numerous and beautiful 
crystallizable salts. If aniline be treated with chlorine-gas, the action goes 
farther, trichlor aniline, C I2 (H 4 C1 3 )N, being produced, a volatile crystalline 
body which has no longer any basic properties. The corresponding bromine- 
compounds have also been formed and described. 

Nitraniline. — If nitrobenzol be heated with fuming nitric acid, or, still 
better, with a mixture of that acid and oil of vitriol, it is converted into a 
substance called binilrobenzol, containing C ]2 H 4 N 2 O g , or nitrobenzol in which 
an additional equivalent of hydrogen is replaced by the elements of hyponi- 
tric acid (see page 399). W T hen this is dissolved in alcohol and subjected to 
the reducing action of sulphide of ammonium in Zinin's process, it furnishes 
a new substance of basic properties, nitraniline, having the constitution of a 
hyponitric acid substitution-product of ordinary aniline. The attempts to 
prepare it direct from aniline by means of nitric acid were unsuccessful, the 
principal product being usually carbazotic acid. Nitraniline forms yellow, 
acicular crystals, but little soluble in cold water, although easily dissolved 
by alcohol and ether. When warmed it exhales an aromatic odour, and 
melts. At a higher temperature it distils unchanged. By very gentle heat 
it may be sublimed without fusion. It is heavier than water, does not affect 
test-paper, and like chlor- and bromaniline fails to give with hypochlorite 
of lime the characteristic reaction of the normal compor.ud. Nitraniline 
forms crystallizable salts, of which the hydrochlorate is the best known. 
This substance contains the elements of aniline with an equivalent of hy- 
drogen replaced by hyponitric acid, or C ]2 H 6 N 2 4=: C, 2 (H 6 N0 4 )N. 

Ct/aniline is formed by the action of cyanogen upon aniline ; it is a crys- 



ORGANIC BASES OF ARTIFICIAL ORIGIN. 461 

talline substance capable of combining with acids like aniline, but very prone 
to decomposition. Cyaniline contains C 14 H 7 N 2 =C 12 H 7 NCy. Hence it is 
formed b}' the direct union of 1 eq. of cyanogen and 1 eq. of aniline. 

Melaniline. — The action of dry chloride of cyanogen upon anhydrous ani- 
line gives rise to the formation of a resinous substance, which is the chlo- 
rine-compound of a very peculiar basic substance to which the name me- 
laniline has been given. Dissolved in water and mixed with potassa, the 
above salt furnishes melaniline in form of an oil, which rapidly solidifies to 
a beautiful crystalline mass. Melaniline contains C 26 H 13 N 3 . The following 
equation represents its formation : — 

2C 12 H 7 N+C 2 NC1=C 26 H 14 N 3 C1. 

Melaniline, when treated with chlorine, bromine, iodine, or nitric acid, 
yields basic substitution-products, in which invariably 2 eq. of hydrogen are 
displaced. It combines with 2 eq. of cyanogen. 

The constitution of the substitution-products of aniline is readily intelli- 
gible ; it is evident that these substances owe their origin to a double sub- 
stitution, namely, first, of 1 equivalent of hydrogen in ammonia by phenyl; 
and, secondly, of one or several equivalents of hydrogen in phenyl by 
chlorine, bromine, &c. The arrangement of the elements may be conveni- 
ently illustrated by the following formulse : — 

Ammonia NET 3 

Aniline NH 2 ,C 12 Hg 

Chloraniline NH 2 ,C 12 (H 4 C1) 

Bromaniline NH 2 ,C 12 (H 4 Br) 

Bibromaniline NH 2 ,C l2 (H 3 Br 2 ) 

Tribrom aniline NH 2 ,C, 2 (H 2 Br 3 ) 

Nitraniline NH 2 ,C l2 (H 4 N0 4 ) 

The constitution of cyaniline and melaniline is not so readily understood. 
Aniline-compounds corresponding to the amides and amido gen- acids, &c. — In 
describing the ammonia-salts of various acids, attention has been repeatedly 
called to the power possessed by many of them to yield several new groups 
of compounds by the loss of a certain amount of water (see pages 313 and 
415). These groups are perhaps best elucidated by the derivatives of oxalic 
acid- 

NH 4 0,C 2 3 — 2HO = C 2 2 N 2 H 

Neutral oxalate of Oxamide. 

ammonia. 

NH 4 0,C 2 3 ,HO,C 2 3 — 2HO = C 2 2 ,NH 2 C 2 3 ,HO 

Binoxalate of ammonia. Oxamic acid. 

NH 4 0,C 2 3 — 4HO = C 2 N 

Neutral oxalate of Oxalonitrile or 

ammonia. cyanogen. 

The terms corresponding to oxamide and oxamic acid have also been ob- 
tained in the aniline-series ; they are produced by the distillation of neutral 
and acid oxalate of aniline, and have been called oxanilide and oxanilic acid. 

Oxanilide = C 14 H 6 N0 2 == C 2 2 ,N(HPyl) 

Oxanilic acid = C 16 H 8 N0 6 = C 2 2 ,N(HPyl),C 2 3 ,HO. 

Compounds analogous to the nitriles have not been obtained in the anilino 
39* 






462 ORGANIC BASBS OF ARTIFICIAL ORIGIN. 

series, and the reason is intelligible if we glance at the formula of oxalate 
of aniline, N(H 3 Pyl)0,C 2 3 . It is obvious that 4 eq. of water cannot be 
eliminated from this salt without touching the hydrogen of the phenyl, i. e., 
without destroying the compouud altogether. A great ruany anilides and 
auilio acids have been formed. 

Aniline-urea. — On passing the vapour of cyanic acid into aniline, the sub- 
stance becomes hot, and solidifies on cooling to a crystalline mass, containing 
C 14 H 8 N 2 2 — C 2 (H 3 Pyl)N 2 2 . This is the composition of aniline-urea. This 
substance, however, does not combine with acids like the ureas (see pages 
4117 and 456), it is only isomeric with the true aniline-urea, which is obtained 
by another process. Among the derivatives of benzoic-acid, nitrobenzok 
acid, C ]4 (H 4 N0 4 )0 3 ,HO, (see page 397,) has been mentioned. The ether of 
this acid, C 4 H 5 0,C u (H 4 N0 4 )0 3 , like oxalic ether, and many other ethers, 
furnishes an amide when treated with ammonia. This substance, nitroben- 
zamide, C 14 (H 4 N0 4 )0 2 ,NH 2 , under the influence of sulphide of ammonium, 
suffers a change, which is perfectly analogous to that of nitrobenzol under 
similar conditions (see page 459). The mixture soon deposits sulphur, and 
yields, on evaporation, crystals of aniline-urea. 

C 14 H 6 N 2 6 + 6HS = C 14 H s N 2 2 -j-4HO + 6S 

Nitrobenzamide. Aniline-urea. 

This substance, which was discovered by M. Chancel, combines with nitric 
and hydrochloric acid, and even with bichloride of platinum. 

Bases homologous to Aniline. 
In a former section of this Manual (page 403), a series of hydrocarbons 
has been mentioned, which are homologous to benzol. Each of these sub- 
stances, when treated Avith fuming nitric acid, yields a nitro-substitute cor- 
responding to nitrobenzol, which, under the influence of sulphuretted hydro- 
gen, is converted into a basic compound homologous to aniline. We thus 
obtain the following group : — 

5 H Nitrobenzol, C l2 H 5 N0 4 Aniline, N(H 2 .C 12 H 5 ) 

C U H 7 H Nitrotoluol, C 14 H 7 N0 4 Toluidine, N(H,,C 14 H 7 ) 

Xylol, C 16 H 9 H Nitroxylol, C ]6 H 9 N0 4 Xylidine, N(H 2 ,C I6 H 9 ) 

Cumol, Ci 8 H u H Nitrocumol, C 18 H n N0 4 Cumidine, N(H 2 ,C l8 H n ) 

Toluidine, Ci 4 H 9 N=N(H 2 ,C 14 H 7 )=N(H 2 Tyl). — This is prepared exact/y 
like aniline. 

Toluidine forms colourless platy crystals, very sparingly soluble in water, 
but easily in alcohol, ether, and oils ; it is heavier than water, has an aro- 
matic taste and odour, and a very feeble alkaline reaction. At 104° (40°C) 
it melts, and at 388° (198°C), boils, and distils unchanged; it forms a series 
of beautiful crystallizable salts. 

Xylidine, C 16 H 11 N=N(H 2 ,C ]6 H 9 )=N(H 2 Xyl). — Of this compound little 
more than the existence is known. 

Cumidine, C 18 H 13 N=N(H 2 ,C 18 H, 1 )=N(PI 2 Cyl). — This s-ibstance is an oil 
which boils at 437° (225°C). It forms magnificent salts with the acids. 

The following two bases are likewise closely allied to the group of aniline- 
bases, both by their mode of formation and by their constitution. 

Napiithalidine, C 20 H 9 N=N(H 2 ,C 2o II 7 )=N(H 2 Nyl). — This substance is 
interesting, as being one of the first of its kind produced by Zinin's process. 

It is obtained by the action of sulphide of ammonium upon an alcoholic 
solution of nitronaphthalase, one of the numerous products of the action of 
nitric acid upon the hydrocarbon naphthalin, which will be noticed in the 
last section of the Manual. When pure it forms colourless silky needles, 



ORGANIC BASES OF ARTIFICIAL ORIGIN. 163 

fusible, and volatile without decomposition. It has a powerful, not disagree- 
able odour and burning taste, is nearly insoluble in water, but readily dis- 
solves in alcohol and ether ; the solution has no alkaline reaction. Naph- 
thalidine forms numerous crystallizable salts. 

Chloronicine, C io (H 6 C1)N=NH 2 G 10 (H 4 C1). — A substance of the above 
composition has been lately discovered by Saint Evre, and deserves special 
notice, because it may be viewed as a chloro-substitute of the natural 
alkaloid nicotine (see page 450), which contains C 10 H 7 N. It is obtained by 
the following rather complicated series of reactions. A stream of chlorine 
is passed through a solution of benzoate of potassa to which some free 
alkali has been added, when a deposit forms consisting of chlorate of potassa 
and the potassa-salt of a new chlorinetted acid C 12 (H 4 C1)0 3 ,H0. This acid, 
which is derived from benzoic acid by the removal of 2 eq. of carbon in the 
form of carbonic acid and by the introduction of 1 eq. of chlorine in the 
place of 1 eq. of hydrogen, has received the name of chloroniceic acid. It 
forms cauliflower-like crystals, fusible at 302° (150°C), and boiling at 479° 
(215°C). It is volatile without decomposition ; when submitted to distilla- 
tion with lime it yields a chlorinetted hydrocarbon chloronicene C 10 (H 5 C1), 
which is converted into nit ro chloronicene C 10 ,(H 4 ClNO 4 ) by the action of 
fuming nitric acid. This, lastly, when treated with sulphide of ammonium 
furnishes chloronicine. It forms brown flakes, which dissolve in a great deal 
of water ; the solution, however, has no alkaline reaction. It forms crys- 
tallizable salts with hydrochloric and acetic acids, and a fine platinum-salt. 
The perfect analogy in the derivatives from chloroniceic acid to that of 
aniline and benzoic acid, is obvious from the following table : — 



Benzoic acid C, 4 H 6 4 


Chloroniceic acid 


C 12 (H 5 C1)0 4 


Benzol C ]2 H 6 


Chloronicene 


C 10 (H 5 C1) 


Nitrobenzol C 12 (H 5 XO.) 


jNatrochloronicene 


C 10 (H 4 C1N0 4 ) 


Aniline C^H 5 ,H 2 N 


Chloronicine 


C 10 (H 4 C1)H 2 N. 



Up to the present moment chloronicine has not yet been converted into 
nicotine, nor has nicotine been transformed into chloronicine. 

MIXED BASES. 

In one of the preceding paragraphs it has been mentioned that the several 
hydrogen-equivalents in ammonium may be replaced by different hydro-carbon 
radicals. In fact, on treating aniline or toluidine with bromide, or iodide of 
ethyl, as described under the head of ethylamine, the following series of 
compounds are obtained : 

Aniline N(H 2 Pyl) Toluidine N(H 2 Tyl) 

Ethylaniline N(HPylAe) Ethylotoluidine ^N(HTylAe) 

Biethyianiline X(PylAe 2 ) Biethylotoluidine N(TylAe 2 ) 

Ammonium base N(PylAe 3 )0,HO Ammonium-base 1 N(TylAe 3 )0,HO 

Ethylaniline (ethylophenylamine) and biethtlaniline (biethylopheny- 
lamine) are liquids greatly resembling aniline. They boil respectively at 
399°-2 (204°C) and 416°-5 (213°-5C). The ammonium-base, to which the 
name Oxide of biethylopheny I- ammonium may be given, is soluble in water, 
with a powerful alkaline reaction, corresponding in its general properties to 
oxide of tetrethyl-ammonium (see page 456). The series of bases which 
may be possibly obtained by changing the radicals is almost without limit ; 
even now a considerable variety has been produced, of which however only 

1 Unpublished researches of Messrs R. Morley and John Abel. 



4 G4: BASES OF UNCERTAIN CONSTITUTION. 

a few will be mentioned here, as remarkable for the diversity of the materials 
With which they are constructed. 

Hydrated oxide of triethylamyl-ammonium, C 22 H 27 N0 2 ==N(3C 4 H 5 , 
Ci H u )O,HO = N(Ae ? Ayl)O,HO. Triethylamine (see page 456), when boiled 
with iodide of amyl is slowly converted into a crystalline mass of iodide of 
Triethylamyl-ammonium. The base liberated with protoxide of silver and 
submitted to distillation yields olefiant gas, and 

Biethylamine, C 18 H 21 N= N(2C 4 H 5 ,C 10 H n ) = N(Ae 2 Ayl), a liquid boiling 
at 309°-2 (154°C). This compound is most powerfully attacked by iodide 
of methyl. Both substances immediately solidify to a beautifully crystalline 
iodide from which protoxide of silver separates. 

Hydrated oxide of methylo-biethylamyl-ammonium, C 20 H 25 NO 2 =N 
(C 2 H 3 ,2C 4 H 5 ,C 10 H 1 ,)O,HO=N(MeAe 2 Ayl),O,HO. This substance, which is 
a powerfully alkaline base, soluble in water, when distilled undergoes the 
same decomposition as the other members of the fourth group of bases, 
yielding olefiant gas, and 

Methylethylamylamine, or ammonia, in which 1 eq. of hydrogen is 
replaced by methyl, another by ethyl, and a third by amyl, C ]6 H, 9 N = N(C 2 
H 3 ,C 4 H 5 ,C ]0 H n )=N(MeAeAyl). This is a basic oil of a peculiar aromatic 
odour, boiling at 275° (135°C) and forming crystallizable salt with the acids. 
Ethylamylaniline, C 26 H 21 N = N(C ]2 H5,C 4 H 5 ,C 10 H H ) = N(PylAeAyl).— 
Ethylaniline (see page 403) treated with iodide of amyl yields the iodide 
of the above base, which is separated by distillation with potassa. It is an 
aromatic oil, boiling at 503°-5 (262°C). The action of iodide of methyl upon 
this substance gives rise to a new iodide from which protoxide of silver sepa- 
rates, and 

Hydrated oxide of methyl-ethyl-amylo-phenyl-ammonium, CggH^NOg 
= N(C 2 H 3 ,C 4 H 5 ,C ]0 H n ,C 12 H 5 )O,HO = N(MeAeAylPyl)O,HO. This compound 
is very soluble in water, is powerfully alkaline, and of an extremely bitter 
taste. The composition, established by the examination of a platinum-salt, 
is certainly remarkable, for this compound contains the radicals of not less 
than four different alcohols. 



bases of uncertain constitution 



In addition to the artificial bases which have just been described, several 
others have been formed by processes less simple and less calculated to afford 
a clear insight into their constitution. The destructive distillation of nitro- 
genous substances has furnished a rich harvest of similar substances. A few 
of the most interesting may be briefly mentioned. 

Chinoleine (Leucoline) C,gH 8 N. — Quinine, cinchonine, strychnine, and 
probably other bodies of this class, when distilled with a very concentrated 
solution of potassa, yield an oily product resembling aniline in many respects, 
and possessing strong basic powers ; it is, however, less volatile than that 
substance, and boils at 460° (235°C). When pure it is colourless and has a 
faint odour of bitter almonds. Its density is 1-081. It is slightly soluble in 
water, and miscible in all proportions with alcohol, ether, and essential oils. 
Chinoleine has no alkaline reaction, but forms salts with acids, which, gene- 
rally speaking, do not crystallize very freely. 



BASES OF UNCERTAIN CONSTITUTION. 465 

Bases from Coal-tar Oil. 

Kyanol and lettkol. — The volatile basic bodies described under these 
names have lately been identified, the first with aniline and the second with 
chinoleine. They are separated from the coal-oil by agitating large quanti- 
ties of that liquid with hydrochloric or diluted sulphuric acid, and then dis- 
tilling the acid liquid with excess of potassa or lime. They are readily sepa- 
rated by distillation. 

Picoline C 12 H 7 N. — Dr. Anderson has described under the foregoing name 
a third volatile, oily base, present in certain varieties of coal-tar-naphtha, 
being there associated with aniline, chinoleine, and several other volatile sub- 
stances but imperfectly understood. It is separated without difficulty from 
the two bases mentioned by distillation, in virtue of its superior volatility. 
Picoline, when pure, is a colourless, transparent, limpid liquid, of powerful 
and persistent odour, and acrid, bitter taste. It is unaffected by a cold of 0° 
( — 17°-7C). It is extremely volatile, evaporates rapidly in the air, and does 
not become brown like aniline when kept in an ill-stopped bottle. Picoline 
has a sp. gr. of 0-955, and boils at 272° (133° -3C). It mixes in all propoi*- 
tions with pure water, but is insoluble in caustic potassa and most saline 
solutions. The alkalinity of this substance is exceedingly well marked ; it 
restores the blue colour of reddened litmus, and forms a series of crystalliza- 
ble salts. This substance, as seen from the above formula, is isomeric with 
aniline, but numerous characteristic reactions completely distinguish it from 
this body. 

Bases from Animal Oil. 

The oily liquid obtained by the distillation of bones and animal matter 
generally, frequently designated by the term Dippel's oil, contains several 
volatile organic bases. Together with some of the substances already de- 
scribed, such as methylamine, ethylamine, picoline, and analine, Dr. Ander- 
son has found in it a peculiar base. 

Petinine C 8 H n N. — The properties of this substance are very analogous to 
those of biethylamine, and triethylamine. It has the same composition as 
biethylamine, but differs from it by its higher boiling-point, which is 175° 
(79° -5C), that of biethylamine being 133"° (55°C) (see page 455). Some 
chemists are inclined to explain this difference by assuming that petinine is 
an ammonia-base, containing the radical butyl, which was mentioned under 
the head of valeric acid (see page 392), in one word that it is butylamine N(H 2 , 
C 8 H 9 ), homologous to ethylamine. This assumption may be correct, but is 
not as yet supported by any experimental evidence. 

Bases obtained by the action of Ammonia upon Volatile Oils. 

Furfttrine. — When sulphuric acid diluted with an equal bulk of water is 
carefully mixed with twice its weight of wheat-bran, and the adhesive pasty 
mass obtained exposed in a proper vessel to the action of a current of steam 
which is afterwards condensed by a worm or refrigerator, a liquid is obtained 
which holds in solution a peculiar volatile oil, to which the term furfur ole has 
been given. By re-distillation several times repeated, the first half of the 
liquid only being collected, the furfurole can be extracted from the water, 
and then by distillation alone obtained in a state of purity. It has a pale 
yellow colour, and a fragrant odour like that of oil of cassia ; its specific 
gravity is 1-165, and it boils at 325° (162°-8C), distilling unchanged. It dis- 
solves in ail proportions in alcohol and to a very considerable extent in water, 
and is readily destroyed by strong acids and caustic alkalis, especially when 
aided by heat. Furfurole contains C 5 H 2 0„. The specific gravity of its vapour 
is 3-493. 



466 BASES OF UNCERTAIN constitution. 

The product of furfurole is very greatly increased and the operation much 
facilitated by previously depriving the bran of all starch, glutin, and soluble 
matter by steeping it in a cold dilute solution of caustic potassa, and wash- 
ing and drying by gentle heat or in the sun. Maceration in cold water for 
some time answers the same purpose, owing to the lactic acid formed in that 
case. 

In contact with solution of ammonia, furfurole becomes converted in the 
space of a few hours into a yellowish-white, crystalline, insoluble substance, 
furfurolamide, C, 5 H 6 N0 3 ; this body is slowly decomposed in contact with 
water, and instantly by an acid into ammonia and furfurole. It may be crys- 
tallized from alcohol, however, in which it dissolves without much change. 
When boiled with a somewhat dilute solution of caustic potassa, no ammonia 
is disengaged, but the substance is slowly dissolved if the quantity of liquid 
be considerable, and the solution deposits on cooling small, white, silky 
needles of a substance having the same composition as furfurolamide itself. 
There is no other product. This new body, to which the name fur/urine has 
been given, is a powerful organic base, forming with acids, a series of beau- 
tiful crystallizable salts, and decomposing at a boiling heat the saline com- 
pounds of ammonia. Furfurine is very sparingly soluble in cold water, but 
dissolves in about 135 parts at 212° (100°C). Alcohol and ether dissolve it 
freely ; the solutions have a strong alkaline reaction. It melts below the 
boiling point of water, and when strongly heated inflames and burns with a 
red and smoky light, leaving but little charcoal. Its salts are intensely 
bitter. Furfurine contains in 1 equivalent CggH^NgOg. 1 

Fucusine. — By treating several varieties of fucus with sulphuric acid in 
exactly the same manner as in the preparation of furfurole, Dr. Stenhouse 
obtained a series of substances, which he designates by the terms fucusol, 
fucusamide, and fucusine. They have exactly the same composition as the 
corresponding terms in the furfurole-series, and also most of their properties, 
but differ in some details. 

Amarine (benzoline). — The hydrobenzamide of M. Laurent, C 42 rT ]8 "N„, 
produced by the action of ammonia on pure bitter-almond-oil (see page 400), 
when long boiled with a solution of caustic potassa, suffers the same kind of 
change as furfurolamide, becoming entirely converted into a new body iso- 
meric with hydrobenzamide, having the characters of a salt-base, and to 
which the preceding name has been given. Precipitated by ammonia from 
a cold solution of the hydrochlorate or sulphate, amarine separates in white 
curdy masses, which when washed and dried become greatly reduced in 
volume. In this state it is singularly electric by friction with a spatula. It 
is insoluble in water, but dissolves abundantly in alcohol ; the solution is 
highly alkaline to test-paper, and if sufficiently concentrated deposits the 
amarine on standing, in the form of small, colourless, prismatic crystals. 
Below 212° (100°C) it melts, and on cooling assumes a glassy or resinous 
condition. Strongly heated in a retort, it decomposes with production of 
ammonia, and a volatile oil not yet examined, and a new body, pyrobenzolin, 
which appears to be a neutral substance, insoluble in water, dissolved by 
boiling alcohol, and containing a large quantity of nitrogen. It is fusible 
by moderate heat, and on cooling becomes a mass of colourless radiating 
needles or plates. The salts of amarine are mostly sparingly soluble : the 
sulphate, nitrate, and hydrochlorate are crystallizable and very definite. 
Amarine contains C 42 H, 8 N 2 . 

Thiosinnamine. — The volatile oil distilled from black mustard-seed, C 8 IT 5 
NS 2 , which will be noticed farther on, in contact with solution of ammonia, 

1 This remarkable substance, the nearest approach to the native alkaloids yet made, was 
discovered by the author of this Manual. — Eds. 



BASES OF UNCERTAIN CONSTITUTION. 4G7 

yields a compound having the characters of an organic base, and forming 
colourless, prismatic crystals, bitter in taste and soluble in water. The 
solution does not affect test-paper. It melts when heated, but cannot be 
sublimed. Acids combine with it, but form no crystallizable salts: the double 
salts of the hydrochlorate with bichloride of platinum and corrosive subli- 
mate are the most definite. This substance contains sulphur ; its formula is 
G 8 H 8 N 2 S r It is the only product of the action of ammonia on the oil. 

Thiosinnamine is decomposed by metallic oxides, as protoxide of lead, 
with production of a metallic sulphide and a new body of basic properties, 
free from sulphur, called sinnamine. This latter substance crystallizes very 
slowly from a concentrated aqueous solution in brilliant, colourless crystals 
which contain water. It has a powerful bitter taste, is strongly alkaline to 
test-paper, and decomposes ammoniacal salts by boiling. With the excep- 
tion of the oxalate, it forms no crystallizable salts. Sinnamine contains in 
the crystallized state C 8 H 6 N 2 ,HO. 

When mustard-oil is treated with protoxide of lead or baryta, the whole 
of the sulphur is withdrawn, and carbonic acid and another basic substance 
produced, which, when pure, crystallizes in colourless plates, soluble in water 
and in alcohol ; the solution has a distinct alkaline reaction. Sinapoline, the 
body so formed, contains C ^H^NjOg. 

Bases from Aldehyde. 

Thialdine — The crystalline compound of aldehyde with ammonia (see 
page 369), is dissolved in 12 to 16 parts of water, mixed with a few drops of 
caustic ammonia, and then the whole subjected to a feeble stream of sul- 
phuretted hydrogen. After a time the liquid becomes turbid and deposits a 
white crystalline substance, which is the body in question. It is separated, 
washed, dissolved in ether, and the solution mixed with alcohol and left to 
evaporate spontaneously, by which means the base is obtained in large, regu- 
lar, rhombic crystals, having the figure of those of common gypsum. The 
crystals are heavier than water, transparent and colourless. They refract 
light strongly. The substance has a somewhat aromatic odour, melts at 
110° (43°-3C), and volatilizes slowly at common temperatures. It distils 
unchanged with the vapour of water, but decomposes when heated alone. It 
is very sparingly soluble in water, easily in alcohol and ether. It has no 
action on vegetable colours, but dissolves freely in acids, forming crystalli- 
zable salts. Heated with hydrate of lime it yields chinoleine. Thialdine 
contains C I2 H l3 NS 4 . 

A very similar compound containing selenium exists. 

Alanine. — This substance is likewise obtained from aldehyde. It Has 
been only recently discovered by Strecker, who obtained it in a reaction, 
which promises many interesting results. If an aqueous solution of the am- 
monia-compound of aldehyde be treated with hydrocyanic and hydrochloric 
acid, chloride of ammonium is formed, together with hydrochlorate of ala- 
nine. On adding to this solution a mixture of alcohol and ether, the greater 
portion of the chloride of ammonium is precipitated ; the filtrate is then 
treated with protoxide of lead to remove a small quantity of ammonium and 
h}'drochloric acid, and separated from the lead by sulphuretted hydrogen. 
The liquid thus obtained deposits feathery crystals of alanine. The compo- 
sition of alanine is C 6 H 7 N0 4 , and its formation represented by the equation : — 

C 4 H 4°2 + HC 2 N + 2HO=C 6 H 7 N0 4 

Aldehyde. Hydrocyanic Alanine, 

acid. 



468 APPENDIX TO THE ORGANIC BASES. 

Alanine crystallizes in rhombic prisms of the lustre of mother-of-pearl. They 
are pretty soluble in cold, but more so in boiling water ; the solution has a 
sweetish taste, but no effect upon vegetable colours. Alanine is a weak base; 
as yet only a crystalline nitrate has been obtained, but several combinations 
with metallic oxides have been produced. This substance has the same com- 
position as lactamide (see page 351), urethane (see page 358), and sarcosine, 
which will be described in the section on the components of the animal body. 
But it is only isomeric with these substances, from which it differs in its 
physical and chemical properties. The most interesting feature in the his- 
tory of alanine is its behaviour with nitrous acid. Under the influence of 
this reagent it is converted into lactic acid, identical in every respect with 
that obtained in the fermentation of sugar (see page 349). This reaction is 
represented by the following equation : — 

C 6 H 7 N0 4 -fN0 3 =C 6 H 5 O s ,HO+2N-j-HO 
Alanine. Lactic acid. 



APPENDIX TO THE ORGANIC BASES. 



All the numerous members of this extensive group, which have been con- 
sidered in the preceding section, invariably contain nitrogen. Recent re- 
searches, however, have shown that two series of analogous substances exist 
which contain phosphorus and antimony, in the place of nitrogen. These 
remarkable compounds, which are not yet sufficiently known, will be briefly 
noticed in the subsequent paragraphs. 

Phosphorus-bases. 

If a current of chloride of methyl (see page 382) be passed over a layer 
of phosphide of calcium (see page 241), heated to about 356° (180°C), a 
mixture of several phosphoretted bodies is produced, which are partly liquid 
and partly solid. M. Paul Thenard, who has investigated this subject, has 
separated from this mixture three compounds, containing carbon, hydrogen, 
and phosphorus, which he believes to correspond to the three hydrides of 
phosphorus (see page 166). 

Phosphoretted Phosphoretted 

hydrogens. methyl-bodies. 

T 2 H P 2 C 2 H 3 =P 2 Me 

PH 2 P2C 2 H 3 =Pi\Ie 2 

PB 3 P3C 2 H 3 =PMe 3 . 

As far as can be seen from the results obtained by M. Thenard, which 
have not yet been published in detail, the two last substances are powerful 
bases analogous to the bases of the nitrogen-series. These substances are 
very readily decomposed, one of them is even spontaneously inflammable, 
so that their preparation and study has been attended with great difficulty 
and even danger, circumstances which sufficiently account for the insuffi- 
ciency of the description. It is evident that the last body is the phospho- 
retted analogue of trimethylamine, triethylamine, and triamylauiine, and 
the question arises whether the second may not be viewed as the phospho- 
retted bimethylamine, and whether farther researches will not establish the 
existence of the whole series of the phosphoretted bases corresponding to 
ihe compound ammonia? previously described. 



APPENDIX TO THE ORGANIC BASES. 4G9 

Antimony-bases. 

Among tLe derivatives of alcohol, a compound of antimony with 3 eq. of 
ethyl has been briefly noticed see page (438) under the name of stibethyl. 
The composition of this remarkable compound approximates it to triethyla- 
mine. 

SriotWe NAe, {"mSS*"}*"* 

A closer examination has shown that this substance differs in many points 
from triethylamine, but that in one very essential character, the two sub- 
stances agree in the mosr perfect manner. 

The properties of stibethyl are the following ; it is a transparent, very 
mobile liquid, of a penetrating odour of onions. It boils at 3-17° (158°-3C). 
In contact with atmospheric air, it emits a dense white fume and frequently 
even takes fire, burning with a white brilliant flame. It combines directly 
with 2 eq. of oxygen, sulphur, chlorine, and iodine. 

Binoxide of stibethyl, SbAe 3 2 , forms a viscid transparent mass soluble in 
water and alcohol. It is extremely bitter and not poisonous. This sub- 
stance cannot be volatilized without decomposition. Binoxide of stibethyl 
combines with acids, giving rise to the formation of crystallizable salts con- 
taining 2 eq. of acid. 

Bisulphide of stibethyl, SbAe 3 S 2 . — Beautiful crystals of silvery lustre, so- 
luble in water and alcohol. Their taste is bitter, and their odour similar to 
that of mercaptan. The solution of this compound exhibits the deportment 
of an alkaline sulphide ; it precipitates the solution of the metals as sul- 
phides, a soluble salt of stibethyl being formed at the same time. This de- 
portment, indeed, affords the simplest means of preparing the salts of stibe- 
thyl. 

Bichloride of stibethyl, SbAe 3 Cl 2 . — Colourless liquid of the odour of oil of 
turpentine. 

Biniodide of stibethyl, SbAe 3 T 2 . — Colourless needles of intensely bitter 
taste. 

The analogy of stibethyl with triethylamine is best exhibited in its deport- 
ment with iodide of ethyl. The two substances combine to a new iodide, 
containing SbAe 4 I, from which a powerful alkaline base may be separated 
by the action of protoxide of silver. This substance, which must evidently 
be analogous to oxide of tetrethyl-ammonium, 

NAe 4 0,H0 SbAe 4 0,HO, 

has not yet been minutely examined. 

A series of analogous substances exist in the methyl-series. They have 
been examined by M. Landolt, who has described several of its compounds, 
separated the methyl-antimony-base corresponding to oxide of tetrethyl- 
ammonium. 

The iodide, SbMe 4 T, produced by the action of iodide of methyl upon 
stibmethyl, crystallizes in white six-sided tables, which are easily soluble in 
water and alcohol, and slightly soluble in ether. It has a very bitter taste, 
and is decomposed by the action of heat. When treated with protoxide of 
silver, it yields a powerfully alkaline solution exhibiting all the properties 
of potassa, from which, on evaporation, a white crystalline mabs, the hydrate 
of the base, SbMe 4 0,HO, crystallizes. This compound forms an acid salt 
with sulphuric acid, which crystallizes in tables. 
+ HO,S0 3 . 
40 



470 ORGANIC COLOURING PRINCIPLES. 



SECTION VI. 
ORGANIC COLOURING PRINCIPLES. 



The organic colouring principles are substances of very considerable prac- 
tical importance in relation to the arts ; several of them, too, have been 
made the subjects of extensive and successful chemical investigation. With 
the exception of one red dye, cochineal, they are all of vegetable origin. 

The art of dyeing is founded upon an affinity or attraction existing 
between the colouring matter of the dye and the fibre of the fabric. In 
•woollen and silk this affinity is usually very considerable, and to such tissues 
a permanent stain is very easily communicated, but with cotton and flax it 
is much weaker. Recourse is then had to a third substance, which does 
possess in a high degree such affinity, and with this the cloth is impregnated. 
Alumina, sesquioxide of iron, and oxide of tin are bodies of this class. 

When an infusion of some dye-wood, as logwood, for example, is mixed 
with alum and a little alkali, a precipitate falls, consisting of alumina in 
combination with colouring matter, called a lake; it is by the formation of 
this insoluble substance within the fibre that a permanent dyeing of the 
cloth is effected. Such applications are termed mordants. Sesquioxide of 
iron usually gives rise to dull, heavy colours ; alumina and oxide of tin, 
especially the latter, to brilliant ones. It is easy to see, that, by applying 
the mordant partially to the cloth, by a wood-block or otherwise, a pattern 
may be produced, as the colour will be removed bv washing from the other 
portions. 

INDIGO. 

Indigo is the most important member of the group of blue colouring 
matters. It is the product of several species of the genus indiyofera, which 
grow principally in warm climates. When the leaves of these plants are 
placed in a vessel of water and allowed to ferment, a yellow substance is 
dissolved out, which by contact of air becomes deep blue and insoluble, and 
finally precipitates. This, washed and carefully dried, constitutes the indigo 
i/f commerce. It is not contained ready-formed in the plant, but is pro- 
duced by the oxidation of some substance there present. Neither is the 
fermentation essential, as a mere infusion of the plant in hot water deposits 
"ndigo by standing in the air. 

Indigo comes into the market in the form of cubic cakes, which, rubbed 
ith a hard body, exhibit a copper-red appearance; its powder has an in- 
tensely deep blue tint. The best is so light as to swim upon water. In 
addition to the blue colouring matter, or true indigo, it contains at least half 
its weight of various impurities, among which may be noticed a red resinous 
matter, the indiyo-red of Berzelius ; these may be extracted by boiling the 
powdered indigo in dilute acid, alkali, and afterwards in alcohol. 

Pure indigo is quite insoluble in water, alcohol, oils, dilute acids, and 
alkalis ; it dissolves in about 15 parts of concentrated sulphuric acid, forming 



INDIGO. 471 

a deep blue pasty mass, entirely soluble in water, and often used in dyeing; 
this is sulphindylic or sulphindigotic acid, a compound analogous to sulphovinic 
acid, capable of forming with alkaline bases blue salts, which, although easily 
soluble in pure water, are insoluble in saline solutions. If an insufficient 
quantity of sulphuric acid has been employed, or digestion not long enough 
continued, a purple powder is left on diluting the acid mass, soluble in a 
large quantity of pure water. The Nordhausen acid answers far better for 
dissolving indigo than ordinary oil of vitriol. Indigo may, by cautious man- 
agement, be volatilized; it forms a fine purple vapour, which condenses in 
brilliant copper-coloured needles. The best method of subliming this sub- 
stance is, according to Mr. Taylor, to mix it with plaster of Paris, make the 
whole into a paste with water, and spread it upon an iron plate. 1 part in- 
digo, and 2 parts plaster, answer very well. This, when quite dry, is heated 
by a spirit-lamp ; the volatilization of the indigo is aided by .the vapour of 
water disengaged from the gypsum, and the surface of the mass becomes 
covered with beautiful crystals of pure indigo, which may be easily removed 
by a thin spatula. At a higher temperature, charring and decomposition 
take place. 

In contact with de-oxidizing agents, and with an alkali, indigo suffers a 
very curious change ; it becomes soluble and nearly colourless, perhaps re- 
turning to the same state in which it existed in the plant. It is on this prin- 
ciple that the dyer prepares his indigo-vat : — 5 parts of powdered indigo, 10 
parts of green vitriol, 15 parts of hydrate of lime, and 60 parts of water, are 
agitated together in a close vessel, and then left to stand. The hydrated 
protoxide of iron, in conjunction with the excess of lime, reduces the indigo 
to the soluble state ; a yellowish liquid is produced, from which acids pre- 
cipitate the white or de-oxidized indigo as a flocculent insoluble substance, 
which absorbs oxygen with the greatest avidity, and becomes blue. Cloth 
steeped in the alkaline liquid, and then exposed to the air, acquires a deep 
and most permanent blue tint by the deposition of solid insoluble indigo in 
the substance of the fibre. Instead of the iron-salt and lime, a mixture of 
dilute caustic soda and grape-sugar dissolved in alcohol may be used ; the 
sugar becomes oxidized to formic acid, and the indigo reduced. On allowing 
a solution of this description to remain in contact with the air, it absorbs 
oxygen and deposits the indigo in the crystalline condition. 

The following formulas represent the composition of the bodies described: — 



Blue insoluble indigo C l6 H 5 N 2 

White, or reduced indigo 1 C 16 H 6 N 2 

Sulphindylic acid C 16 H 4 N 0,2S0 3 , HO. 



Products of the Decomposition of Indigo. 

The products of the destructive modification of indigo by powerful chemical 
agents of an oxidizing nature are both numerous and interesting, inasmuch 
as they connect this substance in a very curious manner with several other 
groups of organic bodies, especially with those of the salicyl- and phenyl- 
series. Many of them are exceedingly beautiful, and possess very remarkable 
properties. 

Isatin. — One part of indigo reduced to fine powder, and rubbed to a paste 
with water, is gently heated with a mixture of one part of sulphuric acid 
and one part of bichromate of potassa dissolved in 20 or 30 parts of water 

' Properly hydrogenized indigo, if the above be the correct view: white indigo may, how 
ever, be viewed as a hydrate, and blue indigo as an. oxide, of one and the .'ami substance. 

White indigo d 6 H 5 N O-f-HO 

Blue indigo ....- Ci fl H°N O+O 



472 INDIGO. 

The indigo dissolves with very slight disengagement of carbonic acid toward* 
the end, forming a yellow-brown solution, which on standing deposits impure 
isaiin in crystals. These are collected, slightly washed and re-dissolved in 
boiling water; the filtered solution deposits on cooling the isatin in a state 
of purity. Or, powdered indigo may be mixed with water to a thin paste, 
heated to the boiling-point in a large capsule, and nitric acid added by small 
portions until the colour disappears ; the whole is then largely diluted with 
boiling water, and filtered. The impure isatin which separates on cooling is 
washed with water containing a little ammonia, and re-crystallized. Both 
these processes require careful management, or the oxidizing action proceeds 
too far, and the product is destroyed. 

Isatin forms deep yellowish-red prismatic crystals of great beauty and 
lustre ; it is sparingly soluble in cold water, freely in boiling water, and also 
in alcohol. The solution colours the skin yellow, and causes it to emit a 
very disagreeable odour. It cannot be sublimed. Isatin contains the elements 
of indigo plus 2 eq. of oxygen, or C ]6 H 5 N0 4 . 

A solution of potassa dissolves isatin with purple colour ; from this solu- 
tion acids precipitate the isatin unchanged. When boiled, however, the 
colour is destroyed, and the liquid furnishes on evaporation crystals of the 
potassa-salt of a new acid, the isatinic, containing C 16 H 6 N0 5 .HO. In the 
free state this is a white and imperfectly crystalline powder, soluble in 
water, and easily decomposed into isatin and water. 

By chlorine, isatin is converted into the substitution-product chlorisatin, 
C ]6 (H 4 C1)N0 4 , a body closely resembling isatin itself in properties. If an 
alcoholic solution and excess of chlorine be employed, other products make 
their appearance, as chloranile, C 12 C1 4 4 , trichlorophenol, C 12 (H 3 C1 3 )0 2 , and a 
resinous substance. The former of these substances, the position of which 
in the kinone-series has been already noticed (page 449), yields other pro- 
ducts with potassa and ammonia. Bromisatin is easily formed. The changes 
which isatin, and its chlorinetted and brominetted congeners, undergo when 
submitted to the action of fusing hydrate of potassa has been already con- 
sidered in the section on the vegeto-alkalis (see page 459). 

Exposed to the action of sulphuretted hydrogen and sulphide of ammo- 
nium, isatin furnishes several new compounds, as isathyde, sulfesathyde, sulfa- 
sathyde. 

A hot solution of isatin, when treated with sulphide of ammonium, gives 
rise to a deposit of sulphur, a white crystallized substance being produced 
at the same time ; it has received the name of isathyde, and contains C 16 H e 
N0 4 . It is obvious that it bears to isatin the same relation as white to blue 
indigo. If the sulphide of ammonium be replaced by sulphuretted hydro- 
gen, bisulphisathyde, C 16 H 8 N0 2 S 2 , is produced, which is unlike the former; 2 
eq. of oxygen, being replaced by 2 eq. of sulphur. An alcoholic solution of 
potassa converts this into sulphisathyde, C ]6 H 6 N0 3 S, in which only half of the 
oxygen in isatin is replaced by sulphur. Under the influence of cold aque- 
ous solution of potassa, bisulphisathyde yields indin, C 16 H 6 N0 2 , which is iso- 
meric with white indigo. When treated with boiling potassa, indin fixes the 
elements of 2 eq. of water, and becomes indinic acid, C I6 H 7 N0 3 ,H0, the po- 
tussa-salt of which forms fine black needles. 

Ammoniacal gas and solution of ammonia yield with isatin a series of in- 
teresting substances containing the nitrogen of the ammonia in addition to 
that of the isatin. 

Action or chlorine on indigo. — In the dry state chlorine has no action 
whatever on indigo, even at the temperature of 212° (100°C). In contact 
with water, the blue colour is instantly destroyed, and cannot again be re- 
stored. The same thing happens with the blue solution of sulphindylic acid. 
When chlorine is passed into a mixture of powdered indigo and water until 



INDIGO. 473 

the colour disappears, and the product is then distilled in a retort, water 
containing hydrochloric acid and a mixture of two volatile bodies, trichlor- 
aniline, Ci 2 (H 4 Cl 3 )N, and trichlorophenol, C )2 (rr 3 Cl 3 )0 2 , pass over into the 
receiver, while the residue in the retort is found to contain chlorisatin, al- 
ready mentioned, and bichlorisatin, C ]6 (H 3 C1 2 )N0 4 , much resembling that sub- 
stance, but more freely soluble in alcohol. Both these bodies yield acids in 
contact with boiling solution of potassa, by assimilating the elements of water. 

The action of bromine on indigo is very similar. 

Anilic and picric acids. — Anilic or indigotic acid is prepared by adding 
powdered indigo to a boiling mixture of 1 part of nitric acid and 10 parts 
of water, until the disengagement of gas ceases, filtering the hot dark- 
coloured liquid, and allowing it to stand. The impure anilic acid so ob- 
tained is converted into the lead-salt, which is purified by crystallization and 
the use of animal charcoal, and then decomposed by sulphuric acid. Anilic 
acid forms fine white or yellowish needles, which have a feeble acid taste 
and very sparing degree of solubility in cold water. In hot water and in 
alcohol it dissolves easily. It melts when heated, and on cooling assumes 
a crystalline structure. By careful management it may be sublimed un- 
changed. Anilic acid contains C 14 H 4 N0 9 .HO=C I4 (H 4 N0 4 )0 5 ,HO. It has 
been mentioned that the same acid is readily prepared from salicylic acid 
(see page 406). Hence it is more appropriately called nitro-salicylic acid. 

Picric, carbazotic, or nitrophenisic acid, is one of the ultimate products 
of the action of nitric acid upon indigo and numerous other substances, as 
fiilk, wool, several resins, especially that of Xanlhorhcea hastilis (yellow gum 
of Botany Bay), salicin and some of its derivatives, cumarin, and certain 
bodies belonging to the phenyl-series. It may be prepared from indigo by 
adding that substance in coarse powder and by small portions to ten or 
twelve times its weight of boiling nitric acid of sp. gr. 1-43. When the last 
of the indigo has been added, and the action, at first extremely violent, has 
become moderated, an additional quantity of nitric acid may be poured upon 
the mixture, and the boiling kept up until the evolution of red fumes nearly 
ceases. When cold, the impure picric acid obtained may be removed, con- 
verted into potassa-salt, several times re-crystallized, and, lastly, decom- 
posed by nitric acid. In the pure state it forms beautiful pale yellow scaly 
crystals, but slightly soluble in cold water, and of insupportably bitter taste. 
Picric acid is used in dyeing ; it forms a series of crystallizable salts of yel- 
low or orange colour : that of potassa forms brilliant needles, and is so little 
soluble in cold water, that a solution of picric acid is occasionally used as a 
precipitant for that base. The alkaline salts of this acid explode by heat 
with extraordinary violence. The crystals of picric acid contain C ]2 H 2 N 3 
13 .HO. 

If a solution of picric acid be distilled with hydrochlorite of lime, or a 
mixture of chlorate of potassa and hydrochloric acid, an oily liquid of a 
penetrating odour is obtained, having a sp. gr, of 1-665, and boiling between 
237° and 239° (114° and 115°C). The substance, chloropicrin, was disco- 
vered by Stenhouse, who gives the formula C 4 Cl 7 N 2 O, ; MM. Gerhardt and 
Cahours assign to it the formula C 2 C1 3 N0 4 . According to the latter formula, 
which is more probable, chloropicrin would be chloroform, in which the hy- 
drogen is replaced by the elements of hyponitric acid : 

Chloroform C 2 (HC1 3 ) ; Chloropicrin C 2 (N0 4 C1 3 ). 

Products of the action of hydrate of potassa upon indtgo. — One of 
the most remarkable of these, aniline, has been already described (see page 
459). When powdered indigo is boiled with a very concentrated solution of 
caustic potassa, it is gradually dissolved with the exception of some brown- 
ish flocculent matter, and the liquid on cooling deposits yell aw crystals of 
40* 



474 LICHENS. 

the potassa-salt of a new acid, the chrysanilic, which can be procured in a 
purer state, by dissolving the crystals in water, filtering from reproduced 
indigo, and adding a slight excess of mineral acid. Chrysanilic acid can be 
obtained in indistinct crystals from weak alcohol ; it is supposed to contain 
C 28 H 10 N 2 O 5 ,HO, but it is very probable that it is a mixture of several sub- 
stances, especially isatinic acid. 

When this substance is boiled with mineral acids, it is decomposed into 
another new acid, the anthranilic, which remains in solution, and a blue in- 
soluble matter resembling indigo ; a similar effect is slowly produced by the 
action of the air upon an alcoholic solution of chrysanilic acid. Anthranilic 
acid is colourless, sparingly soluble in cold water, easily soluble in alcohol. 
It melts when heated, sublimes under favourable circumstances, but decom- 
poses entirely when heated in a narrow tube into carbonic acid and aniline. 
It contains C ]4 H 6 N0 3 ,HO. By treatment with nitrous acid, anthranilic acid 
is converted into salicylic acid C u H 6 N0 3 ,HO-j-N0 3 =C 14 H 5 5 ,HO-|-HO-f 2N. 

According to M. Cahours, pure indigo can also be converted into salicylic 
acid by fusion with hydrate of potassa ; a particular temperature is required, 
somewhat above 570° (298°C), and the operation is by no means always 
successful. 



Litmus is used by the dyer as a red colouring matter ; the chemist employs 
it in the blue state as a test for the presence of acid, by which it is instantly 
reddened. 

In preparing test-papers for chemical use with infusion of litmus, good 
writing or drawing-paper, free from alum and other acid salts, should be 
chosen. Those sheets which after drying exhibit red spots or patches, may 
be reddened completely by a little dilute acetic acid, and used, with much 
greater advantage than turmeric-paper, to discover the presence of free 
alkali, which restores the blue colour. 

Many lichens, when exposed in a moistened state to the action of ammonia, 
yield purple or blue colouring principles, which, like indigo, do not pre- 
exist in the plant itself. Thus, the Roccella tincloria, the Variolaria orcina, 
the Lecanora tartarea, &c, when ground to paste with water, mixed with 
putrid urine or solution of carbonate of ammonia, and left for some time 
freely exposed to the air, furnish the archil, litmus, and cudbear of commerce, 
very similar substances, differing chiefly in the details of the preparation. 
From these the colouring matter is easily extracted by water or very dilute 
solution of ammonia. 

The lichens have been extensively examined by Schunk, Stenhouse, and 
several other chemists. The whole subject has been lately revised by Dr. 
Strecker, whose formulae have been adopted in the following succinct ac- 
count : — 

Erythric acid. — The lichen Roccella tinctoria, from which the finest kind 
of archil is prepared, is boiled with milk of lime, the filtered solution is pre- 
cipitated by hydrochloric acid, and the precipitate dried and dissolved in 
warm, not boiling, alcohol, from which on cooling crystals of erythric acid are 
deposited. This is a very feeble acid, colourless, inodorous, difficultly solu- 
ble in cold and even in boiling water, readily soluble in ether. Its solution, 
when mixed with chloride of lime, assumes a blood-red colour. Boiled with 
water for some time, erythric acid absorbs 2 eq. and yields picro-erythrin, a 
crystallizable, bitter principle, and a new acid presently to be described, 
which is termed by some chemists lecanoric, by others orsellinic acid. If the 
ebullition be continued, the orsellinic acid undergoes a farther change, being 
converted into a crystalline substance, orcin, of which mention will shortly 
be made. 



LICHENS. 475 

The composition of these various substances is expressed by the following 
formulae : — 

Erythric acid : C 20 H n O 10 

Orsellinic acid C 16 H 8 g 

Picro-erythrin , C 24 H, 6 0, 4 

Orcin C 14 H 8 0* 4 

And the successive changes which occur by ebullition are represented by the 
following equation: — 

2C 20 H- n (Vf2HO = C 16 H 8 8 + C^H^ 
Erythric acid. Orsellinic acid. Picro-erythrin. 

CjeHA = C*HA + 2C0 2 
Orsellinic acid. Orcin. 

Alphaorsellic acid is obtained from the South American variety of 
Roccella tinctoria. The preparation and the properties of this substance are 
perfectly analogous to those of erythric acid. Alphaorsellic acid contains 
C 32 H 14 14 ; by boiling with baryta-water it likewise furnishes orsellinic acid. 

C^H u O M +2HO = ^HgOg 

Alphaorsellic Orsellinic acid, 

acid. 

If the ebullition be continued too long, a great portion of the orsellinic 
acid is converted into orcin. 

Orsellinic acid, formerly frequently called lecanoric acid, whether pre- 
pared from erythric or alphaorsellic acid, forms crystals which are far more 
soluble in water than either of the acids from which it has been prepared. 
Its taste is somewhat bitter. Boiled with water, it yields, as has been 
stated, orcin ; under the influence of air and ammonia, it assumes a beauti- 
ful purple colour. 

If the lichens, instead of being treated with milk of lime, be exhausted 
with boiling alcohol, the erythric and alphaorsellic acids are likewise decom- 
posed ; but instead of orsellinic acid, the ether of this substance, C 4 H 5 0, 
C ]6 H 7 7 , is formed. This ether was formerly described under the name 
pseudo-erythrin until Mr. Schunk pointed out the true nature of the sub- 
stance. Orsellinate of ethyl may be likewise produced by boiling pure 
orsellinic acid with alcohol. It crystallizes in colourless lustrous plates, 
which are readily soluble in boiling water, alcohol, and ether. 

Betaorsellic acid is found in Roccella tinctoria grown at the Cape ; it ia 
obtained like erythric and alphaorsellic acid, which it resembles in proper- 
ties. Betaorsellic acid contains O^HjgO,- ; by boiling with water, it yields 
likewise orsellinic acid, together with hair-like crystals of a silvery lustre, 
of a substance called roccellinin, which has the composition C 18 H 8 7 . 

^34^16^15 — C 16 II 8 0g -j- C ]8 H 8 7 

Betaorsellic acid. Orsellinic acid. Boccellinin. 

The decomposition of betaorsellic acid is obviously analogous to that of 
erythric acid, the roccellinin representing the picro-erythrin. 

Evernic acid is extracted by milk of lime from Evernia prunastri, which 
was formerly believed to contain orsellinic acid. Evernic acid is very diffi- 
cultly soluble even in boiling water ; it assumes a yellow colour with chlo* 



476 LICHENS. 

ride of lime. When boiled with the alkalis, it yields another crystalline 
acid, everninic acid, differing from the preceding by its free solubility in 
boiling water. The composition of evernic acid is represented by the for- 
mula C 34 H ]6 14 , that of everninic acid by C 18 H 10 O 8 . Evernic acid, when 
boiled for a considerable time with baryta, yields orcin ; everninic acid does 
not give a trace of this substance ; it is therefore probable that evernic acid, 
under the influence of alkalis, yields in addition to everninic acid likewise 
orsellinic acid, from which the orcin is derived, and that this decomposition 
is represented by the equation : — 

C34Hi 6 ]4 -|-2HO = C 16 H 8 8 -f- C 18 H 10 O 8 

Evernic acid. Orsellinic acid. Everninic acid. 

Parellic acid. — Lecanora parella contains an acid probably analogous to 
erythric, alphaorsellic, betaorsellic, and evernic acids, the composition of 
which is, however, still unknown. By boiling with baryta it yields orsellinic 
acid and parellic acid, C, 8 H 6 8 . 

Orcin is the general product of decompositions of the acids previously 
described under the influence of heat or alkaline earths. 

Orcin is best prepared by boiling lecanoric or orsellinic acid, pure or im- 
pure, with baryta-water, precipitating the excess of baryta by carbonic acid, 
and evaporating the filtered liquid to a small bulk. It forms, when pure, 
large, square prisms, which have a slightly yellowish tint, an intensely 
sweet taste, and a high degree of solubility both in water and alcohol. When 
heated, orcin loses water and melts to a syrupy liquid which distils un- 
changed. The crystals of orcin contain C 14 H 8 4 ,2HO. 

Orcein. — When ammonia is added to a solution of orcin, and the whole 
exposed to the air, the liquid assumes a dark red or purple tint, by absorp- 
tion of oxygen ; a slight excess of acetic acid then causes the precipitation 
of a deep red powder, not very soluble in water, but freely dissolving in 
ammonia and fixed alkalis, with a purple or violet colour. This is an azo- 
tized substance, formed from the elements of the ammonia and the orcin, 
called orcein; it probably constitutes the chief ingredient of the red dye- 
stuff of the commercial articles before mentioned. The composition of 
orcein is less certain than that of orcin; it probably contains C l4 H 7 N0 6 , 
when its formation from orcin, under the joint influence of oxvgen and 
ammonia, would be represented by the equation : — 

C 14 H 8 4 ,2HO + 60 + NII 3 = C l4 H 7 N0 6 + 6HO 

Orcin. Orcein. 

Other substances are occasionally present in lichens ; thus, the TJsnea 
barbata and several other lichens contain usnic acid, a substance crystallizing 
from alcohol in fine yellowish-white needles with metallic lustre, having the 
formula C 34 H ]8 14 . It gives no orcin by distillation, but a substance similar 
to it, which probably contains C 38 H ]8 6 , and has been designated by the 
name of betaorcin. Its formation, which is attended by an evolution of car- 
bonic acid, is represented by the equation : — 

C3 8 H 18 14 = C^A-MCOa 

Usnic acid. Betaorcin. 

The Farmelia parietina furnishes another new substance, chrysophanic acid, 
crystallizing in fine golden-yellow needles and containing C 10 H 4 O 3 . It is a 
veiy stable substance, and may be sublimed without much decomposition. 



RED AND YELLOW Dl IS. 477 



RED AND YELLOW DYES. 

Cochineal. — This is a little insect, the Coccus cacti, which lives on several 
species of cactus, which are found in warm climates, and cultivated for the 
purpose, as in Central America. The dried body of the insect yields to water 
and alcohol a magnificent red colouring matter, precipitable by alumina and 
oxide of tin ; carmine is a preparation of this kind. In cochineal the colour- 
ing matter is associated with several inorganic salts, especially phosphates 
and nitrogenetted substances. Mr. Warren De La Rue, who has published 
a very elaborate investigation of cochineal, 1 has separated the pure colouring 
matter, which he calls carminic acid, by the following process. The aqueous 
decoction of the insect is precipitated by the acetate of lead, and the impure 
carminate of lead washed and decomposed by hydrosulphuric acid ; the 
colouring matter thus separated is submitted again to the same treatment. 
A solution of carminic acid is thus obtained, which is evaporated to dryness, 
re-dissolved in absolute alcohol, and digested with crude carminate of lead, 
whereby a small quantity of phosphoric acid is separated, and lastly mixed 
with ether, which separates a trace of a nitrogenetted substance. The 
residue now obtained on evaporation is pure carminic acid. It is a purple- 
brown mass, yielding a fine red powder, soluble in water and alcohol in all 
proportions, slightly soluble in ether. It is soluble without decomposition 
in concentrated sulphuric acid, but readily attacked by chlorine, bromine, 
and iodine, which change its colour to yellow. It resists a temperature of 
276°-8 (136°C), but is charred when heated more strongly. Carminic acid 
is a feeble acid. The composition of the substance, dried at 248° (120°C), 
is represented by C 2s H, 4 ]6 , which formula was corroborated by the analysis 
of a copper-compound, CuO,C 2s H ]4 16 . 

By the action of nitric acid upon carminic acid, together with oxalic acid, 
a splendid nitrogenetted acid, crystallizing in yellow rhombic plates, is ob- 
tained. This substance, to which the name nitrococcusic acid was given, is 
bibasie ; it contains C 16 H 3 N 3 I6 ,2HO. It is soluble in cold, and more so in 
boiling water, readily soluble in alcohol and ether. Nitrococcusic acid is 
evidently derived from a non-nitrogenous compound in which part of the 
hydrogen is replaced by the elements of hyponitric acid. Like the sub- 
stances of this class, it explodes when heated. 

In the mother-liquor, from which the carminic acid has been separated, 
Mr. Warren De La Rue discovered a white, crystalline, nitrogenetted sub- 
stance, for which he established the formula C,j,H n N0 6 . This substance is 
identical with tyrosine, which will be mentioned in the section on Animal 
Chemistry. 

Madder. — The root of the Rubia tinctornm, cultivated in southern France, 
the Levant, &c, is the most permanent and valuable of the red dye-stuffs. 
In addition to several yellow colouring matters, which are of little impor- 
tance for the purposes of the dyer, madder contains two red pigments which 
are called alizarin and purpurin. These substances have been the subject of 
very extensive researches by Debus, Higgins, and especially by Schunk. The 
latest papers on madder have been published by Wolff and Strecker, whose 
formulae are quoted in the following abstract. 

Alizarin. — The aqueous decoction of madder is precipitated by sulphuric 
acid, and the precipitate washed and boiled with sesquichloride of aluminum, 
which dissolves the red pigments ; an insoluble brownish residue remaining 
behind. The solution, when mixed with hydrochloric acid, yields a precipi- 
tate consisting chiefly of alizarin, however, still contaminated with purpurin. 
The impure alizarin thus obtained may be farther purified by again throwing 

1 Mem. of the Chem. Soc. vol. iii. p. 451. 



478 RED AND YELLOW DYES. 

down the alcoholic solution with hydrate of alumina, and boiling the preci- 
pitate with a concentrated solution of soda, which leaves a pure compound 
of alumina and alizarin behind. From this the alizarin is separated by 
hydrochloric acid, and re-crystallized from alcohol. Pure alizarin crystal- 
lizes in splendid red prisms, which may be sublimed. It is but slightly solu- 
ble in water and in alcohol, but dissolves in concentrated sulphuric acid with 
a deep red colour. On addition of water, the colouring matter is re-precipi- 
tated unchanged. It is also soluble in alkaline liquids, to which it imparts 
a magnificent purple colour. It is insoluble in cold solution of alum. Ali- 
zarin is the chief colouring matter of madder ; it contains C 20 H 6 O 6 -f-4HO, and 
is a feeble acid ; but a few definite compounds with mineral oxides have been 
prepared, among which a lime-compound, C 20 H 6 O 6 ,8CaO-|-3HO, may be 
quoted. The action of nitric acid upon alizarin gives rise to the formation 
of oxalic acid and phthalic acid, a substance which will again be men- 
tioned among the products of decomposition of naphthalin. 

C 20 II c O 6 +2HO + 8O = 2(C 2 3 ,HO)-f-C 16 H 6 8 

Alizarin. Phthalic acid. 

PuuruniN. — Madder is allowed to ferment and then boiled with a strong 
solution of alum. The solution, when mixed with sulphuric acid, yields a 
red precipitate, which is purified by re-crystallization from alcohol. Purpurin 
thus obtained crystallizes in red needles, which contain C ls H 6 6 -(-2HO, i. e., 
2 eq. of carbon less than alizarin. When treated with nitric acid, pui*purin, 
like alizarin, furnishes oxalic and phthalic acids. Purpurin likewise con- 
tributes to the tinctorial properties of madder, but less so than alizarin. 
Together with alizarin and purpurin, several other substances occur in 
madder, among which may be noticed an orange pigment, rubiacin, convertible 
by oxidizing agents into a peculiar acid, rubiacic acid, a yellow pigment, 
xanthin, a bitter principle, rubian, sugar, pectic acid, and several resins, &c. 

Garancin is a colouring material, which is produced by the action of sul- 
phuric acid upon madder. This substance possesses a higher tinctorial power 
than madder itself. 

The beautiful Turkey red of cotton cloth is a madder-colour : it is given by 
a very complicated process, the theory of which is not perfectly elucidated. 
An abstract of it will be found in Prof. Graham's " Elements of Chemistry." 

Safflower. — This substance contains a yellow and a red colouring matter, 
the latter being insoluble in water, but soluble in alkaline liquids. The saf- 
flower may be exhausted with water acidulated with acetic acid, and the 
solution mixed with acetate of lead, and filtered from the dark-coloured 
impure precipitate. The lead-compound of the yellow pigment may then be 
thrown down by addition of ammonia, and decomposed by sulphuric acid. 
In its purest form the yellow matter forms a deep yellow, uncrystallizablc, 
and very soluble substance, very prone to oxidation. In its lead-compouirj 
it has probably the composition C 2 4H 12 O l3 . 

The red matter or carthamin is obtained from the residual safflower by a 
dilute solution of carbonate of soda ; pieces of cotton wool are immersed in 
the liquid, and acetic acid gradually added. The dried cotton is then digested 
in a fresh quantity of the alkaline solution, and the liquid supersaturated 
with citric acid, which throws down the carthamin in carmine-red flocks. It 
forms, when pure and dry, an amorphous, brilliant, green powder, nearly 
insoluble in water, but soluble in alcohol with splendid purple colour. It 
contains C 14 H 8 7 . 

Brazil-wood and logwood give red and purple infusions, which are largely 
used in dyeing ; the colouring principle of logwood is termed hematoxylin, 



RED AND YELLOW DYES. 479 

and has been obtained in crystals. This substance contains C 40 H 7 O, 5 -f-8HO. 
Acids brighten these colours, and alkalis render them purple or blue. 

Among yellow dyes, quercitron-bark, fustic-wood, and saffron may be men- 
tioned, and also turmeric ; these all give yellow infusions to water, and furnish 
more or less permanent colours. 

Purree or Indian yellow, a body of unknown origin, used in water-colour 
painting, according to the researches of Stenhouse and Erdmann, is a com- 
pound of magnesia with a substance termed purreic or euxanihic acid. The 
latter, when pure, crystallizes in nearly colourless needles, sparingly soluble 
in cold water, and of sweetish bitter taste. It forms yellow compounds with 
the alkalis and earths, and is decomposed by heat with production of a 
neutral crystalline sublimate, purrenone or euzanthone. Purreic acid contains 
C 40 H ]6 O 21 , purrenone C 13 H 4 4 . By the action of chlorine, bromine, and nitrio 
acid, a series of substitution-products are formed. 



Certain of the products of the action of nitric acid upon aloes resemble 
vei\y much some of the derivatives of indigo, without, however, it seems, 
being identical with them. Powdered aloes, heated for a considerable time 
with excess of moderately strong nitric acid, yields a deep red solution, which 
deposits on cooling a yellow crystalline mass. This, purified by suitable 
means, constitutes chrysammic acid; it crystallizes in golden-yellow scales, 
which have a bitter taste, and are but sparingly soluble in water. Its potassa- 
salt has a carmine-red tint, and exhibits a green metallic lustre, like that of 
murexide. The formula of chrysammic acid is not perfectly established. It 
is probably C 14 HN 2 O n ,HO. Like picric acid, it yields with chloride of lime, 
chloropicrin. The mother-liquor from which the chrysammic acid has been 
deposited contains a second acid, the chrysolepic, which also forms golden- 
yellow, sparingly soluble, scaly crystals. The potassa-salt forms small, 
yellow prisms, of little solubility. It explodes by heat. Chrysolepic acid 
contains C ]2 H 2 N 3 O l3 .HO ; it is isomeric and possibly identical with picric acid. 

To these may be added the styphnic acid recently described by MM. 
Boettger and Will, produced by the action of nitric acid of sp. gr. 1-2 upon 
assafcetida and several oilier gum-resins and extracts. Purree, when treated 
with excess of nitric acid, likewise 3 T ields styphnic acid. It crystallizes, 
when pure, in slender, yellowish-white prisms, sparingly soluble in water, 
readily dissolved in alcohol and ether. It has a purely astringent taste, 
and stains the skin yellow. By gentle heat it melts, and on cooling becomes 
crystalline ; suddenly and strongly heated, it burns like gunpowder. It also 
furnishes chloropicrin. The salts of this substance mostly crystallize in 
orange-yellow needles, and explode with great violence by heat. Styphnic 
acid contains CjjILjNgO^HO, i. e., picric acid-r-2 eq. of oxygen. It may be 
viewed as a nitro-substitute of the same acid, C ]2 H 5 3 ,HO, which, by the in- 
troduction of chlorine in the place of hydrogen, furnishes chloroniceic acid 
(see page 463). 

Hypothetical niceic acid Cj 2 H 5 ,0 3 ,HO 

Chlo*oniceic acid C" l2 (H 4 Cl)0 3 ,HO 

Trinitroniceic acid C 12 H 2 (N0 4i )30 3 ,H(X 



4#0 OILS AND FATS. 



SECTION VII. 

OILS AND FATS. 



The oils and fats form an interesting and very natural group of substances, 
which have been studied with great success. The vegetable and animal fats 
agree so closely in every respect, that it will be convenient to discuss them 
under one head. 

Oily bodies are divided into volatile and fixed: the former are capable of 
being distilled without decomposition, the latter are not. When dropped or 
spread upon paper, they all produce a greasy stain ; in the case of a vola- 
tile oil, this stain disappears when the paper is warmed, which never happens 
with a fixed fatty substance. All these bodies have an attraction, more or 
less energetic, for oxygen : this in some cases reaches such a height as to 
occasion spontaneous inflammation, as in the instance of large masses of cot- 
ton or flax moistened with rape or linseed oil. The effect of this absorption 
of oxygen leads to a farther classification of the fixed oils into drying and 
non-drying oils, or those which become hard and resinous by exposure to air, 
and those which thicken slightly, become sour and rancid, but never solidify. 
To the first class belong the oils used in painting, as linseed, rape, poppy- 
seed, and walnut ; and to the second, olive and palm-oils, and all the oils and 
fats of animal origin. The parts of plants which contain the largest quanti- 
ties of oil are, in general, the seeds. Olive-oil is, however, obtained from the 
fruit itself. The leaves of many plants are varnished on their upper surface 
with a covering of waxy fat. Among the natural orders, that of the cruciferce 
is conspicuous for the number of oil-bearing species. 

The fixed oils in general have but feeble odour, and scarcely any taste ; 
whenever a sapid oil or fat is met with, it is invariably found to contain some 
volatile oily principle, as in the case of common butter. They are all insolu- 
ble in water, and but slightly soluble in alcohol, with the exception of castor- 
oil ; in ether and in the essential oils, on the other hand, they dissolve in 
large quantity. 

The consistence of these substances varies from that of the thinnest olive- 
oil to that of solid, compact suet; and this difference proceeds from the vari- 
able proportions in which the proximate solid and fluid fatty principles are 
associated in the natural product. All these bodies may, in fact, by mere 
mechanical means, or by the application of a low temperature, be separated 
into two, or sometimes three, different substances, which dissolve in, or mix 
with each other, in all proportions. Thus, olive oil exposed to a cold of 
40° (4 0, 5C) deposits a large quantity of crystalline solid fat, which may be 
separated by filtration and pressure ; this is termed margarin, from its pearly 
aspect. That portion of the oil which retains its fluidity at this, or even an 
inferior degree of cold, has received the name olein or elain. Again, a solid 
animal fat may, by pressure between folds of blotting-paper, be made much 
harder, more brittle, and more difficult of fusion. The paper becomes im- 
pregnated with a permanently fluid oil, or olein, while the solid part is found 
to consist of a mixture of two solid fats, one resembling the margarin of olive- 



OILS AND FATS. 481 

oil, and the other having a much higher melting-point, and other properties 
Which distinguish it from that substance ; it is called stearin. 

These remarks apply to all ordinary oils and fats : it is, however, by no 
means pi'oved that the olein and margarin of all vegetable and animal oils 
are identical; it is very possible that there may be essential differences 
among them, more especially in the case of the first-named substance. 

Fixed fatty bodies, in contact with alkaline solutions at a high tempera- 
ture, undergo the remarkable change termed saponification. When stearin, 
margarin, or olein, are boiled with a strong solution of caustic potassa or 
soda, they gradually combine with the alkali, and form a homogeneous, 
viscid, transparent mass, or soap, freely soluble in warm water, although in- 
soluble in saline solutions. If the soap so produced be afterwards decom- 
posed by the addition of an acid, the fat which separates is found completely 
changed in character ; it has acquired a strong acid reaction when applied 
in a melted state to test-paper, and it has become soluble with the greatest 
facility in warm alcohol ; it is in fact a new substance, a true acid, capable 
of forming salts, and a compound ether, and has been generated out of the 
elements of the neutral fat under the influence of the base. Stearin, when 
thus treated, yields stearic acid, margarin gives margaric acid, olein gives 
oleic acid, and common animal fat, which is a mixture of the three neutral 
bodies, affcrds by saponification by an alkali and subsequent decomposition 
of the soap, a mixture of the three fatty acids in question. These bodies 
are not, however, the only products of saponification ; the change is always 
accompanied by the formation of a very peculiar sweet substance, called 
glycerin, which remains in the mother-liquor from which the acidified fat has 
been separated. The process of saponification itself proceeds with perfect 
facility in a close vessel ; no gas is disengaged ; the neutral fat, of whatso- 
ever kind, is simply resolved into an alkaline salt of the fatty acid, or soap, 
and into glycerin. 1 

Stearin and stearic acid. — Pure animal stearin is most easily obtained 
by mixing pure mutton-fat, melted in a glass flask, with several times its 
weight of ether, and suffering the whole to cool. Stearin crystallizes out, 
while margarin and olein remain in solution. The soft pasty mass may then 
be transferred to a cloth, strongly pressed, and the solid portion still farther 
purified by re-crystallization from ether. It is a white friable substance, in- 
soluble in water, and nearly so in cold alcohol ; boiling spirit takes up a 
small quantity. Boiling ether dissolves it with great ease, but when cold 
retains only =~-^ of its weight. The melting-point of pure stearin, which is 
one of its most important physical characters, may be placed at about 130° 
(54°-5C). 

When stearin is saponified, it yields, as already stated, glycerin and stearic 
acid. The latter crystallizes from hot alcohol in milk-white needles, which 
are inodorous, tasteless, and quite insoluble in water. It dissolves in its 
own weight of cold alcohol, and in all proportions at a boiling heat; it is 
likewise soluble in ether. Alkaline carbonates are decomposed by stearic 
acid. Exposed to heat, it fuses, and at a higher temperature, if air be ex- 
cluded, volatilizes unchanged. The melting-point of stearic acid is about 
158° (70°C). 

Margarin and margaric acid. — The ethereal mother-liquor from which 
stearin has separated in the process just described yields on evaporation a 
soft-solid mixture of margarin and olein with a little stearin. By compres- 

1 We arc indebted to M. Chevreul for the first series of scientific researches on the fixed 
oils and fats, and on the theory of saponification. These admirable investigations are detailed 
in the early volumes of the ' : Annales de Chimie et de Physique," and were afterwards pub- 
lished in a separate form in 1823, under the title of " Ecchcrchcs chimiques sur les Corps gras 
cCOriginc animate." 
41 



482 OILS AND FATS. 

sion between folds! of blotting-paper, and re-solution in ether, it is rendered 
tolerably pure. In this state margarin very much resembles stearin ; it is, 
however, more fusible, melting at 11G° (4G°-6C), and very much more solu- 
ble in cold ether. By saponification it yields glycerin and margaric acid. 
The properties of this last-named substance resemble in the closest manne? 
those of stearic acid; it is different in composition, however, more solubk 
in cold spirit, and has a lower melting-point, viz., 140° (60°C) or there- 
abouts. Its salts also resemble those, of stearic acid. 

A more or less impure mixture of stearic and margaric acids is no\t 
very extensively used as a substitute for wax and spermaceti in the manu- 
facture of candles. It is prepared by saponifying tallow by lime, decom- 
posing the insoluble salt so formed by boiling with dilute sulphuric acid, and 
then pressing out the fluid or oily portion from the acidified fat. 

The solid part of olive-oil is said to be a definite compound of true mar- 
garin and olein, inasmuch as its melting-point, 68° (20°C), is constant; it 
gives by saponification a mixture of margaric and oleic acids. 

Olein and oleic acid. — It is doubtful whether a perfectly pure olein has 
yet been obtained ; the separation of the last portions of margarin, with 
which it is alwaj'S naturally associated, is a task of extreme difficulty. Any 
fluid oil, animal or vegetable, which has been carefully decolorized, and 
filtered at a temperature approaching the freezing-point of water, may be 
taken as a representative of the substance. Oleic acid much resembles olein 
in physical characters, being colourless and lighter than water, but it has 
usually a distinct acid reaction, a sharp taste, and is miscible with alcohol 
in all proportions. When submitted to the action of nitric acid, it yields 
almost the whole series of acids, of which formic, acetic, propionic, butyric, 
&c, are members, and which has been mentioned in a previous section of 
this work (see page 395). 

When stearic or margaric acid, or ordinary animal fats, are exposed to 
destructive distillation, they yield margaric acid, a fatty body incapable of 
saponification, termed murgarone, a liquid carbide of hydrogen, and various 
permanent gases. The neutral fats furnish besides an extremely pungent 
and even poisonous, volatile principle, called acrolein, described farther on. 

In the manufacture of ordinary soaps both potassa and soda are used ; the 
former yielding soft, and the latter hard soaps. Animal and vegetable fats 
are employed indifferently, and sometimes resin is added. 

Composition of the preceding Substances. — The following are the formulae at 
present assigned to the fatty acids in question: they are chiefly founded on 
investigations made at Giessen. 

Stearic acid C 68 H 66 5 .2HO 

Margaric acid C 68 H 66 6 ,2HO. 

Margaric is thus seen to differ from stearic acid in containing 1 eq. of oxy- 
gen more, and stearic acid can actually be converted into margaric by the 
action of oxidizing agents. Stearic acid is bibasic, and in its crystallized 
state contains 2 eq. of water. Margaric acid, as represented by the above 
formula, is likewise bibasic, but many chemists consider it as a monobasic 
acid CgjHggO^HO : its bibasic nature being, in fact, by no means so we'd 
established as that of stearic acid. The subject requires farther examina- 
tion, especially since an opinion has lately been expressed, that stearic and 
margaric acids are isomeric modifications of the same acid. 1 

1 According to Huntz, margaric acid is a mixture of stearic and palmitic acids, and that 
one part of stearic acid mixed with 9-10 parts of palmitic acid (melting at 144°; C2°-2C), pro- 
duced a compound fusing at 140°(("0°C), and possessing all the properties and ultimate com- 
position of margaric acid. Moreover, when margaric acid ohtained from mutton-fat -was acted 
on by acetate of baryta, the first precipitate gave an acid melting at 135°o (57°C), and soliJi- 



OILS AND FATS. 483 

Ol^ic acid from almond-oil, butter, and beef-suet, gave results agreeing 
pwitt^ «vell, and leading to the formula C 36 H 33 3 ,HO, the oleic acid of goose- 
fa.;, and olive- oil, having the same composition. Former researches had led 
to different results which are explained by the extreme proneness to oxida- 
tion of the substance itself. The oleic acid obtained from linseed-oil appears 
to differ from the preceding substance; its analysis having led to the for- 
mula C 46 H 3S 5 ,H0. (?) 

Margarone probably contains CjjsHggO, or margaric acid minus 1 eq. of 
carbonic acid. 

The composition of stearin, margarin, and oleine is most safely deduced 
from a comparison of that of the acids to which they give rise, and of gly- 
cerin. 

Margaric, stearic, and oleic acids have many properties in common : their 
salts much resemble each other, those of the alkalis being soluble in pure 
water when warm, but not in saline solution. A large quantity of cold water 
added to an alkaline margarate or stearate occasions the separation of a 
crystalline, insoluble acid salt. The margarates, stearates. and oleates of 
lime, baryta, and the oxides of the metals proper are insoluble in water. 
They are easily obtained by double decomposition, and in some few cases by 
direct action on the neutral fat. A solution of soap in alcohol is sometimes 
used as a test for the presence and quantity of lime, &c, in waters under 
examination (see page 241). 

Glycerin. — This substance is very readily obtained by heating together 
olive or other suitable oil, protoxide of lead, and water, as in the manufacture 
of common lead-plaster ; an insoluble soap of lead is formed, while the gly- 
cerin remains in the aqueous liquid. The latter is treated with sulphuretted 
hydrogen, digested with animal charcoal, filtered, and evaporated in vacuo 
at the temperature of the air. In a pure state, glycerin forms a nearly colour- 
less and very viscid liquid, of sp. gr. 1-27, which cannot be made to crystal- 
lize. It has an intensely sweet taste, and mixes with water in all propor- 
tions; its solution does not undergo the alcoholic fermentation, but when 
mixed with yeast and kept in a warm place, it is gradually converted into 
propionic acid (see page 377). Grycerin has neither basic nor acid proper- 
ties. Exposed to heat, it volatilizes in part, darkens, and becomes destroyed, 
one of its products of destruction being a substance possessing a most power- 
fully penetrating odour, which is called acrolein (see page 345). Nitric acid 
converts it into oxalic acid. 

Glycerin is composed of C 6 H 8 6 . 

Glycerin combines with the elements of sulphuric acid, forming a compound 
acid, the sulpho glyceric, C 6 H 7 5 ,2S0 3 ,HO, which gives soluble salts with lime, 
baryta, and protoxide of lead. 1 

Palm and cocoa oils. — These substances, which at the common tempera- 
ture of the air have a soft-solid or buttery consistence, are now largely con- 
sumed in this country. Palm-oil is the produce of the Elais guianensis, and 
comes chiefly from the coast of Africa. It has, when fresh, a deep orange- 
red tint, and a very agreeable odour ; the colouring matter, the nature of 

ficd •without crystallizing ; the other one, after repeated crystallization, melted at 142°-7 (61 a 5 
C), crystallized in needles, and exhibited the properties of palmitic acid. — R. B. 

1 Glycerin has been combined with acids. To effect this, the acid is mixed with the glyce- 
rin, and a current of hydrochloric acid passed through the mixture for several hours. This 
is set aside for periods, varying from a few days to several weeks. The hydrochloric acid is 
saturated by carbonate of soda, and then washed repeatedly. 

These compounds are oleaginous, nearly or quite insoluble in water, do not unite with 
carbonated, but are slowly decomposed hy caustic alkali, the glycerin separating unaltered 

Acetate of glycerin (acetine) has the appearance of a limpid, colourless oil, of a taste, at 
first, sweet, them sharp, the odour of acetic ether, and is volatile, without decomposition. 

Valerate of glycerin (valerene) resembles phoceniue, with which it should be identical. 

Benzoate of glycerin (benzoiciue) has an aromatic and peppery taste. — R. B. 



484 OILS AND FATS. 

•which is unknown, is easily destroyed by exposure to light, especially at a 
high temperature, and also by oxidizing agents. The oil melts at 80° (26° -6 
C). By cautious pressure it may be separated into a fluid olein and a solid 
substance, palmitin, which, when purified by crystallization from hot ether, 
is perfectly white, fusible at 118° (47° -8C), soluble to a small extent only in 
boiling alcohol, and convertible by saponification into palmitic acid. The latter 
resembles in the closest manner margaric acid, and has the same melting- 
point; it differs in composition, however, containing H 32 C 3 j0 3 ,HO. By keep- 
ing, palm-oil seems to suffer a change similar to that produced by saponifi- 
fication; in this state it is found to contain traces of glycerin, and a 
considerable quantity of oleic acid, together with a solid fatty acid, first 
supposed to be margaric, which is probably palmitic acid. The oil becomes 
harder and rancid, and its melting-point is raised at the same time. Cocoa- 
oil, extracted from. the kernel of the common cocoa-nut, is white, and has a 
far less agreeable smell than the preceding. It contains olein and a solid fat, 
often used as a substitute for tallow in making candles, which by saponifica- 
tion gives a crystallizable fatty acid, cocinic acid, having the usual properties 
of these bodies, and melting at 95° (85°-5C). It is composed of C^H^O^HO. 
Both this and palmitic acid are monobasic. 

The solid vegetable fat from the Myristica moschata contains a volatile oil, 
a fluid olein, and a solid, crystallizable, fatty principle ; this, when saponified, 
which occurs with difficulty, yields myristic acid. This substance has been 
examined by Dr. Playfair; it melts at 120° (48°-8C), and contains C 28 H 27 3 , 
110. It is monobasic. 

Cacao-butter, extracted from the crushed beans by boiling with water, 
yields by saponification a fatty acid, identical, according to Dr. Stenhouse, 
with the stearic acid from animal fat. 

Elaidin and elaidic acid. — When olive-oil is mixed with a small quantity 
of nitrous acid, nitric acid containing that substance, or solution of nitrate 
of mercury made in the cold, it becomes after a few hours a yellowish, soft- 
solid mass, which, pressed and treated with alcohol, furnishes a peculiar 
white, crystalline, fatty substance, termed elaidin. It resembles a neutral 
fat in properties, melts at 90° (32° -2C), dissolves with difficulty in boiling 
alcohol, easil}* in ether, and is resolved by saponification into glycerin and 
elaidic acid, which much resembles margaric acid. Oleic acid is directly con- 
vertible by nitrous acid into elaidic acid. It is not every kind of oil which 
furnishes elaidin ; the drying oils, as those of linseed, poppy-seed, walnuts, 
&c, refuse to solidify; almonds, olive, and castor-oils possess the property 
in a high degree. 

Elaidic acid appears to have the same composition as oleic acid, or CgglLjg 
3 ,H0. 

Suberic, succinic, and sebacic acids. — Suberic acid has long been known 
as a product of the oxidation of cork by nitric acid (see page 315) ; succinic 
acid is obtained by the dilution of amber, a fossil resin. Recently both have 
been produced by the long-continued action of nitric acid upon stearic and 
margaric acids. Suberic acid is a white, crystalline powder, sparingly so- 
luble in cold water, fusible and volatile by heat; it contains C 16 H 12 6 ,2HO. 
Succinic acid forms regular, colourless crystals, soluble in 5 parts of cold, 
and in half that quantity of boiling water ; it is also fusible and volatile 
without decomposition, and contains C 8 H 4 6 ,2HO. The remarkable pro- 
duction of this substance from malic acid by a process of fermentation has 
been already mentioned (see page 415). Sebacic acid is a constant product 
of the destructive distillation of oleic acid, olein, and all fatty substances 
containing tlose bodies; it is extricated by boiling the distilled matter with 
water ; it has also been lately formed by the action of potassa on castor-oil 
(see page 488). It forms small pearly crystals resembling those of benzoic 



OILS AND FATS. 485 

aoid. It has a faint acid taste, is but little soluble in cold water, melts when 
heated, and sublimes unchanged. Sebacic acid is composed of C 10 H 8 O 3 ,HO 
or C 20 II 16 O 6 ,2HO. 

Butter; volatile acids or butter. — Common butter chiefly consists of 
a solid crystallizable, and easily fusible fat, a fluid oily substance, and a 
yellow colouring matter, besides mechanical impurities, as casein. The oily 
part appears to be a mixture of olein and a peculiar odoriferous fatty prin- 
ciple, bulyrin, not yet isolated, which by saponification yields four distinct 
volatile acids, the butyric, the caproic, the chprylic, and the capric : these are 
most easily obtained by saponifying butter with potassa or soda, adding an 
excess of sulphuric acid, and distilling. The acid watery liquid obtained 
may then be saturated with an alkali, evaporated to a small bulk, and then 
distilled with excess of sulphuric or phosphoric acid in a retort. The mixed 
acids are separated by taking advantage of the unequal solubility of their 
baryta-salts ; the less soluble salts of the mixture, amounting to about J» 
of the whole mass, contain capric and caprylic acids ; the lai'ger and more 
soluble portion, the caproic and butyric acids. 

Butyric acid, when pure, is a thin colourless liquid, of pungent rancid 
odour and sour taste. It is miscible in all proportions with water and alcohol. 
Its density is 0-963, and it boils and distils unchanged at 327° (164°C). It 
is attacked by chloi'ine, with production of oxalic acid and of a chlorinetted 
compound not examined. Butyric acid contains C 8 H 7 3 ,HO. 

Caproic acid forms a colourless liquid, of sp. gr. 0-922, boiling at 388° -4 
(•198°C) ; it has a feeble odour, somewhat resembling that of acetic acid, and 
is much less soluble in water than butyric acid. It contains C 12 H n 3 ,HO. 
The artificial formation of this acid from cyanide of amyl has been already 
noticed (see page 390). Caproic acid has been lately submitted to the action 
of the galvanic current. Messrs. Brazier and Gossleth have proved that it. 
is analogous to that of valeric acid, and that the principal product is the hydro- 
carbon amyl C 10 H n previously obtained by Dr. Frankland by the action of 
zinc upon iodide of amyl (see page 390). 

Caprylic acid is chiefly remarkable for exhaling a powerful and disgusting 
odour of perspiration. It contains C, 6 H, 5 3 ,HO. This acid has been lately 
obtained by a very interesting reaction, namely, by the oxidation of the new 
caprylic alcohol discovered by M. Bouis among the products of decomposition 
of castor oil (see page 488). 

Capric acid much resembles the caproic ; it has a mixed odour of acetic 
acid and the smell of the goat, and is very sparingly soluble in water. Its 
formula is C^HjgO^HO. 

The simple relation existing between the formulae of the volatile acids of 
butter, which are all members of the series of fatty acids, has been already 
pointed out (see page 395). 

These acids exist ready formed in rancid butter and in cheese, associated 
with valeric acid. They are produced in small quantity by the saponifica- 
tion of most animal and some vegetable fats, and are generated, as has been 
mentioned already (see page 482), together with other products, by the 
action of nitric acid upon oleic acid. Butyric acid has been observed also 
as a product of the spontaneous decomposition of fibrin, and pre-exists in the 
leguminous fruit known as St. John's bread. 

"Whale and seal oil yield by saponification a volatile acid greatly resembling 
the preceding, called phocenic or delphinic acid ; it was formerly believed to 
be a peculiar acid, but it is according to recent experiments nothing but 
valeric acid. 

Butyric acid has acquired a certain degree of importance from the curious? 
discovery of M. Pelouze, that sugar, under particular circumstances, is sus 
ceptible of becoming converted into that substance. A tolerably strong 
41* 



480 OILS AND FATS. 

solution of common sugar mixed -with a small quantity of casein and some 
chalk, and exposed for some time to a temperature of 95° (35°C), yields, 
by a species of fermentation, in which the casein is the active ferment, a 
large amount of butyrate of lime ; carbonic acid and hydrogen gases are 
extricated during the whole period. This change may be thus expressed — 

C 24 H 23 28 = 4HO-f8H-f-8CO a + 2(C 8 H 7 3 ,HO) 

Grape-sugar. Butyric acid. 

The mixture directed for lactic acid answers well (see page 350) ,- lactate 
of lime is first formed in large quantity, and afterwards gradually dissolved 
and converted into butyrate, which may be decomposed by sulphuric acid 
and distilled. This is an exceedingly interesting case of the half-artificial 
formation of an animal product. 

Wax. — Common bees-wax, freed from its yellow colouring matter by 
bleaching, may be separated by boiling alcohol into two different proximate 
principles, cerin and myricin. The first is a white crystalline substance, 
soluble in about 16 parts of boiling spirit, and melting at 144° (62° -2C) ; it 
is the more abundant of the two. It is easily saponified by a solution of 
caustic potassa. According to Brodie's valuable experiments it consists 
chiefly of cerotic acid C 54 H 53 3 ,HO, which belongs to the series of fatty 
acids (see page 395). The same body in a very interesting form of combi- 
nation exists in Chinese wax, which, according to Brodie, is a compound 
ether containing cerotic acid combined with the ether of cerotylic alcohol 
C 54 H 55 0,HO. It may be viewed as cerotate of oxide of cerotyl C 34 H 55 0, 
C^H-jjOg corresponding to the acetic ether of the wine-alcohol-series. When 
heated with potassa it undergoes the changes peculiar to compound ethers, 
yielding on the one hand cerotate of potassa, and on the other hand cerotylic 
alcohol. Myricin is very much less soluble in alcohol, and rather more 
fusible. It is saponified with difficulty by a dilute solution of caustic 
potassa, palmitic acid C 32 H 31 3 ,HO (see page 484), combines with the po- 
tassa, and a substance C 60 H 6l O,HO, belonging to the series of alcohols, is 
set free, which has been termed melissic alcohol. Hence myricin is like- 
wise a compound ether, namely, palmitate of oxide of melissyl C 92 H s2 4 = 

^60 66^> ^32 " 33^3" 

Spermaceti. — The soft-solid matter found in very large quantity in a 
remarkable cavity in the head of the spermacetic whale, when submitted to 
pressure, yields, as is well known, a most valuable fluid oil, and a crystal- 
line, brownish substance, which, when purified, becomes the beautiful snow- 
white article of commerce, spermaceti. This substance appears, by the 
most recent experiments, to be a neutral fatty body of the constitution of 
compound ethers, and not, as formerly supposed, a mixture of several proxi- 
mate principles. It melts at 120° (48° -8C), and when cooled under favour- 
able circumstances, forms distinct crystals. Boiling alcohol dissolves it in 
small quantity, and ether in much larger proportion. Spermaceti is sapo- 
nified with great difficulty: two products are obtained, a substance C^H^C^ 
belonging to the series of alcohols (see page 394), to which the name cetylic 
(ethalic) alcohol has been given, and cetylic (etkalic) acid C 32 H 32 4 ; the first is 
a crystallizable fat, whose melting-point is nearly the same as that of 
spermaceti itself, but its solubility in alcohol is much greater; it is also 
readily sublimed without decomposition. Cetylic acid stands to cetylic 
alcohol in the same relation as acetic acid to ordinary alcohol, and may be 
actually procured from the latter by oxidation ; it resembles in many re- 
spects margaric acid. By oxidation by nitric acid, spermaceti yields a large 
quantity of succinic acid. 

Spermaceti is composed of C 64 TT 60 O 4 ==C a2 TJ 33 O,C, ; JT 3] O 3 ; it is cetylate of 



OILS AND FATS. 487 

oxide of c-etyl, and represents in the cetyl-series the acetic ether of the 
common alcohol-series. 1 

Cholesterix. — This substance is found in small quantity in various parts 
of the animal system, as in the bile, in the brain and nerves, and in the 
blood ; it forms the chief ingredient of biliary calculi, from which it is easily 
extracted by boiling the powdered gall-stones in strong alcohol, and filtering 
the solution while hot ; on cooling, the cholesterin crystallizes in brilliant, 
colourless plates. It has the characters of a fat, is insoluble in water, taste- 
less and inodorous ; it is freely soluble in boiling water, and also in ether. 
It altogether resists saponification. Cholesterin melts at 278° (136°C), and 
contains probably C 26 H 22 0. 

Cantharidin, the active principle of the Spanish fly, may be here men- 
tioned. It is a colourless, crystallizable, fatty body, extracted by ether or 
alcohol from the insect ; it is insoluble in water and dilute acids, and vola- 
tile when strongly heated. The vapour attacks the eyes in a very painful 
manner. Cantharidin contains C 10 H 6 O 4 . 

Acrolein. — When a neutral fat is subjected to destructive distillation, it 
furnishes, as already mentioned, among other products, an excessively vola- 
tile acrid substance, which attacks the eyes and the mucous membrane of 
the nose most distressingly. As the neutral fats alone yield this body, and 
the fatty acids never, it is known to arise from the elements of the glycerin ; 
and glycerin itself under certain circumstances may be made to produce 
acrolein abundantly. It is best prepared by distilling glycerin with bisul- 
phate of potassa ; both the preparation and purification are attended with 
great difficulties. 

Pure acrolein is a thin, colourless, highly volatile liquid, lighter than 
water, and boiling at 126° (52°-9C). Its vapour is irritating beyond descrip- 
tion. It is sparingly soluble in water, freely in alcohol and ether. Accord- 
ing to M. Redtenbacher it contains C fi H 4 2 . 

When exposed for some time to the air, or when mixed with oxide of 
silver, acrolein oxidizes with avidity, and passes into acrylic acid, which re- 
sembles in very many particulars acetic and propionic acids ; it contains 
C 6 H 3 3 ,HO. Acrolein by keeping undergoes partial decomposition, yielding 
a white, flocculent, indifferent body, disacryle ; the same substance is some- 
times produced together with acrylic acid by exposure to the air. In con- 
tact with alkalis, acrolein suffers violent decomposition, producing, like 
aldehyde, a resinous body. 

The action of sulphuric acid upon olive-oil has been studied by M. Fremy. 
"When the oil is slowly and cautiously mixed with half its volume of concen- 
trated sulphuric acid, all rise of temperature being avoided, a homogeneous 
liquid is obtained, which, when mixed with a little water, separates into two 
layers, the undermost consisting of sulpho-glyceric and free-sulphui'ic acid, 
and the upper and syrupy portion of two compound acids, the sulphomaryaric 
and sulpholeic. These latter dissolve in a large quantity of water, but after 
some time undergo decomposition into sulphuric acid and several new fatty 
acids, to which the names metamargaric, hydromaryaric, hydromaryaritic, 
metoleic, and hydroleic were given. The first three are derived from the ele- 

1 According to the investigations of Ileintz, the composition of spermaceti is of a very 
coir pi ex character, consisting of a series of acids differing in constitution hy C2H2 combined 
vy.'th ethal. viz. : — 

Margethal = margarate of oxide of cetyl C34H 33 Oa ; Cg 2 II 3 30 

Palmethal = palmitate C32Hj n 3 .C32H 33 

Cetethal = cetate C3oII,9C :i .C S 2H 3S 

Myristethal = myristate C2feH 2 70 3 .C32H-3 3 O 

Cocethal = cocinate Csel^sOs^^HasO.— R. B 



488 OILS AND FATS. 

merits of the sulphomargaric acid; they are solid and crystallizable, and 
much resemble ordinary margaric acid, differing slightly from that substance 
and from each other in their melting-points, degree of solubility in alcohol, 
&c. The metoleic and hydroleic acids are fluid, and are derived from the 
sulpholeic acid of the mixture. They yield carbonic acid and liquid hydro- 
carbons by destructive distillation. The composition of these fatty acids is 
yet uncertain, but in all probability they only differ from margaric and oleic 
acids by the elements of water. The action of sulphuric acid upon the oil 
is thus somewhat similar to the effect of saponification, the neutral fat being 
resolved into margaric and oleic acids and glycerin, the whole of which 
then combine with the elements of sulphuric acid to form compounds belong- 
ing to the large group of substances of which sulphovinic acid is the typical 
member. 

The sulphuric saponification of fatty bodies is now carried out on a, very 
large scale for producing cheaper varieties of "stearin candles." For this 
purpose, inferior fatty bodies, such as palm-oil, are mixed with 5 or 6 per 
cent, of concentrated sulphuric acid, and exposed to a temperature of 350° 
(177°C) produced by overheated steam. After cooling, the black mass thus 
obtained crystallizes to a tolerably solid fat, which is washed once or twice 
with water, and then submitted to distillation by the aid of steam, heated to 
about 560° (293° -5C). The product of the distillation, which is beautifully 
white, may be at once used for making candles ; frequently, however, it un- 
dergoes the processes of cold and hot pressing, whereby a much more solid 
fat is obtained. 

Castor oil, which differs in some respects from the ordinary vegetable 
oils, yields, by oxidation with nitric acid, a peculiar product, namely, a vola- 
tile fatty acid to which the term cenanthylic has been applied. It forms a 
colourless, oily liquid of aromatic odour and burning taste, and slightly 
soluble in water. It refuses to solidify at a very low temperature, and can- 
not be distilled alone without some decomposition, although its vapour passes 
over readily with that of water. This body has distinct acid properties, 
forms a series of salts and an ether, and contains C 14 H 13 3 ,HO. Under the 
influence of the galvanic current it undergoes a decomposition similar to 
that of valeric acid, according to Messrs. Brazier and Gossleth, the principal 
product being, together with a hydrocarbon containing equal equivalents of 
carbon and hydrogen, an oily substance C 12 H 13 , boiling at 395°-6 (202°C), to 
which the name caprogl has been given, and which may be viewed as the 
radical of the alcohol of caproic acid C 12 If 13 0,HO, still to be discovered. 

Castor-oil has lately become the source of a new alcohol in the hands of 
M. Bouis. According to his researches, there is present in castor-oil a pecu- 
liar oleic acid, ricinoleic acid, which contains C 36 PT 33 5 ,HO, i. e., 2 eq. of 
oxygen more than common oleic acid. If this acid, or more conveniently 
castor-oil itself, be heated with solid hydrate of potassa, an oily liquid distils 
over, boiling at 356° (180°C). which is the alcohol of caprylic acid. It con- 
tains C 18 H 17 0,HO, and is readily converted into caprylic acid (see page 485), 
by treatment with oxidizing agents. The residue in the retort contains 
sebacate of potassa. This transformation is represented by the following 
equation : — 

QjellAHO + 2(KO,HO) -_= 2KO,C 20 H 16 O 6 -f C 16 H 17 0,HO -f 211 

Bicinoleic acid. Sebacate of potassa. Caprylic alcohol. 

VOLATILE OILS. 

The volatile oils of the vegetable kingdom are exceedingly numerous ; they 
are secreted by plants, and confer upon their flowers, fruits, leaves, and 



VOLATILE OILS. 489 

wood their peculiar odours. These substances are mostly procured by dis- 
tilling the plant, or part of the plant, with water; their points of ebullition 
always lie above that of water; nevertheless, at 212° (100°C) the oils emit 
vapour of very considerable tension, which is carried over mechanically, and 
condensed with the steam. The milky, or turbid liquid obtained, when left 
at rest, separates into oil and water. Sometimes the oil is heavier than the 
water, and sinks to the bottom ; sometimes the reverse happens. 

The volatile oils, when pure, are colourless ; they very frequently, how- 
ever, have a yellow, and in rarer cases, a green colour, from the presence 
of impurity. The odour of these substances is usually powerful, and their 
taste pungent and burning. They resist saponification completely, but when 
exposed to the air frequently become altered by slow absorption of oxygen, 
and assume the character of resins. They mix in all proportions with fat 
oils, and dissolve freely both in ether and alcohol ; from the latter solvent 
they are precipitated by the addition of water. As already mentioned, the 
volatile oils communicate a greasy stain to paper, which disappears by warm- 
ing ; by this character any adulteration with fixed oils can be at once de- 
tected. A solid, crystalline matter, corresponding to the margarine of the 
common oils, frequently separates from these bodies ; it bears the general 
name of slearoptene, and differs probably in almost every case. 

The essential oils may be conveniently divided into three classes; viz., 
those consisting of carbon and hydrogen only ; those consisting of carbon, 
hydrogen, and oxygen ; and those containing in addition sulphur and nitrogen. 

Oils composed of Carbon and Hydrogen. 

Oil, or essence of turpentin. — This substance may be taken as the type 
or representative of the class ; it is obtained by distilling with water the soft 
or semi-fluid balsam called in commerce crude turpentine, which exudes from 
various pines and firs, or flows from wounds made for the purpose in the 
wood. The solid product left after distillation is common resin. Oil of tur- 
pentin, when farther purified by rectification, is a thin, colourless liquid, 
of powerful and well-known odour: its density in the liquid state is 0-865, 
and that of its vapour 4-764; it boils at 312° (155°-5C). In water it dis- 
solves to a small extent, and in strong alcohol and ether much more freely ; 
with fixed oils it mixes in all proportions. Strong sulphuric acid chars and 
blackens this substance ; concentrated nitric acid and chlorine attack it with 
such violence that inflammation sometimes ensues. 

Oil of turpentin is composed of C 5 H 4 or C 20 H 16 . 

With hydrochloric acid the oil forms a curious compound, which has been 
called artificial camphor from its resemblance in odour and appearance to that 
substance. It is prepared by passing dry hydrochloric acid gas into the 
pure oil, cooled by a freezing mixture. After some time, a white, crys- 
talline substance separates, which may be strained from the supernatant 
brown and highly acid liquid, and purified by alcohol, in which it dissolves 
very freely. This substance is neutral to test-paper, does not affect nitrate 
of silver, and sublimes without much decomposition ; it contains C 20 H I7 ,C1, 
or perhaps C 20 H 16 ,HC1. The dark mother-liquid contains a somewhat similar, 
but fluid compound. Different specimens of oil of turpentin yield very 
variable quantities of these substances, which may, perhaps, arise from the 
co-existence of two very similar and isomeric oils in the ordinax^y article. 
"When these hydrochlorates are decomposed by distillation with lime, they 
yield liquid oily products differing in some particulars from the original oil 
of turpentin, but have the same composition as that substance. That from 
the solid has received the name of camphylene, and that from the liquid com 
pound terebylene. The hj'pothetical and non-isolable modifications of the oi] 



490 VOLATILE OILS. 

supposed to exist in the solid comphor are termed respectively camphene and 
terebene. 

Anothef isomeric compound, colophene, is produced by distilling oil of tur- 
pentin with coucentrated sulphuric acid. It is a viscid, oily, colourless 
liquid, of high boiling-point, and exhibiting by reflected light a deep bluish 
tint, — a phenomenon often remarked in bodies of this class. 

Bromine and iodine also form compounds with oil of turpentin. 

Oil of turpentin is very largely used in the arts, in painting, and as a sol- 
vent for resins in making varnishes. 

Bottles in which rectified oil of turpentin, not purposely rendered anhy- 
drous, has been preserved, are often studded in the interior with groups of 
beautiful, colourless, prismatic crystals, which form spontaneously. These 
have the composition of a hydrate of oil of turpentin. These crystals contain 
<V,H 16 H 6 6 . 

Oil op lemons is expressed from the rind of the fruit, or obtained by dis- 
tillation with water. This oil differs very much from the last in odour, but 
closely resembles it in other respects. It has the same composition as oil 
of turpentin, and forms with hydrochloric acid two compounds ; one solid 
and crystalline, the other fluid. The solid contains C 10 H 8 HC1. 

The oils of orange-peel, bergamot, pepper, cubebs, juniper, capivi, elemi, the 
laurel-oil of Guiana, the East Indian grass-oil, and the principal part of hop- 
oil, are hydrocarbons, isomeric with the oils of turpentin and lemons. 

Essential Oils containing Oxygen. 

The essential oils containing oxygen are very numerous, and in fact make 
up the great bulk of the bodies of this class employed in medicine and per- 
fumery. They are seldom homogeneous, and in consequence do not often 
exhibit fixed boiling-points. Some of these oils have been made the subjects 
of much chemical research, but the majority yet require examination. Three 
of the most interesting, viz., those of bitter almonds, cinnamon, and the 
Spircea ulmaria have been already described. 

Oil of aniseed. — The oil distilled from the seeds of the Pimpinella anisam 
consists of two substances, one of which is a fluid oil, and the other a solid 
crystalline substance, so abundant as to cause the whole to solidify at a tem- 
perature of 50° (10°C). By pressure between folds of bibulous paper and 
crystallization from alcohol, the solid essence may be obtained pure. It 
forms colourless pearly plates, more fragrant in odour than the crude oil, 
which melt when gently heated, and distil at a high temperature. It con- 
tains C 30 H 12 O 2 . This substance is attacked energetically by chlorine, bro- 
mine, and nitric acid ; it combines with hydrochloric acid, but is unaffected 
by solution of caustic potassa. With bromine the solid essence yields a 
Avhite inodorous crystallizable compound, bromanisal, containing C 20 (H 9 Br 3 )O 2 . 
The action of chlorine is more complex, several successive compounds being 
produced. With sulphuric acid two products are obtained, a compound acid 
analogous to sulphovinic acid, and a white, solid neutral substance, anisoin, 
isomeric with the essence. 

The products of the action of nitric acid vary with the strength of the 
acid employed; the most important are hydride of anisyl ; anisic acid, a sub- 
stance very much resembling salicylic acid in properties, sparingly soluble 
in cold water, freely in alcohol and ether; nitranisic acid, a yellowish-white, 
crystalline sparingly-soluble powder ; and nilraniside, a resinous body pro- 
duced by fuming nitric acid. 

The hydride of anisyl in a pure state is a yellowish oily liquid, having an 
uromatic odour of hay ; it is heavier than water, and boils at 400° (254°-5C). 
Caustic potassa, concentrated and boiling, slowly decomposes it ; with fused 



VOLATILE OILS. 491 

hydrate of potassa, it is instantly converted into anisic acid with disengage 
nient of hydrogen ; air and oxidizing bodies in general produce the same 
effect. Ammonia forms with it a crystalline compound analogous to hydro- 
benzaraide. Hydride of anisyl contains C 16 H 8 4 . 

Anisic acid contains C ]6 H 7 5 ,HO, i. e., hydride of anisyl and 2 eq. of 
oxygen. When treated with an excess of lime or baryta, it suffers a decom 
position, analogous to that of benzoic and salicylic acid, losing 2 eq. of cai*- 
bonic acid, and being converted into an oxygenated oil, boiling at 802° 
(150°C), to which the name anisol has been given. 

C 16 H 7 5 ,HO-f-2CaO=2(CaO,C0 2 ) + C ]4 H g 2 

Anisic acid. Anisol. 

Nitranisic acid is the nitro-substitute of anisic acid ; it contains C 16 (II e 
N0 4 )0 5 ,HO. 

The solid portion of the oils of bitter fennel and badian is identical with 
that of oil of aniseed. The fluid component of the fennel-oil is isomeric 
with oil of turpentin. 

Draconic acid, obtained by the action of nitric acid upon the oil of Arte- 
misia dracunculus, is identical with anisic acid. 

The various substances belonging to this group are homologous to th« 
members of the salicyl-sei'ies, described in a former part of the Manual 
(see page 404), as may be seen from the following comparison : — 

Hydride of salicyl C, 4 H 6 4 ; C ]6 H 8 4 Hydride of anisyl. 

Salicylic acid C 14 H 6 6 ;C l6 H 8 6 Anisic acid. 

Ni ida a !:?.: L .:.. ( : n !:l... } c » { \ } °* ■• c * { \ } °. ™~— ««■ 

Phenol (hydrate of phe- ~] n TJ n n tt r\ \ • i 

nyl) .....} C i2 H 6 2 ; G 14 H 8 2 Anisol. 

Oil of cuMin is a mixture of two bodies, separable in great measure by 
distillation, cymol, a liquid hydrocarbon, containing C 20 H 14 , the most volatile 
portion of the oil, and cuminol, a colourless transparent oil, of powerful odour, 
easily changed in the air, and only to be distilled in a current of carbonic acid 
gas. Cuminol contains C 20 H ]2 O 2 , and is consequently isomeric with the solid 
essence of aniseed. By oxidation, this substance, which is homologous to oil 
of bitter almonds, yields cumic acid, a white, fatty, volatile substance, insolu- 
ble in water, having but little odour, and crystallizing in prismatic tables. 
It contains C 20 H 11 O 3 ,HO (see homologues of benzoic acid, page 403). 

Oil of cedar-wood, in like manner, contains two substances, a solid crys- 
talline compound, having the formula C 32 H 26 2 , and a volatile liquid hydro- 
carbon, cedrene, C^H^, which can also be obtained by distilling the solid, 
with anhydrous phosphoric acid. 

Oil of gaultheria procumbens. — This very remarkable substance is now 
known in commerce under the name of winter-green-oil ; it consists almost 
wholly of a definite principle which distils unchanged at 435° (223° -8C), and 
contains, according to the analysis of M. Cahours, C 16 H 8 6 . When mixed with 
dilute caustic potassa, it solidifies to a crystalline mass, which is a potassa- 
salt, gaultherate of potassa, and from which the oil may be separated again 
unchanged on the addition of an acid. When distilled, however, with a con- 
centrated solution of caustic potassa, the oil of gaultheria is resolved into 
salicylic acid and wood-spirit, thus exactly resembling in its behaviour the 
compound ethers which have been described in a previous section of the 
Manual (see page 352). This oil is, in fact, a veritable compound etker, 
salicylate of oxyde of methyl, C 2 N 3 0,C 14 H 5 5 =C ]6 H 8 6 , furnished by nature 
herself. With ammonia the oil yields salicylamide, C 14 II 7 N0 4 =C 14 H 5 4 ,NH 2 , 
isomeric with anthranilic acid (see page 474), which is converted by fuming 



492 VOLATILE OILS. 

nitric acid into the nitro-substitute, nitro-salicjdamide (anilamide) C, 4 (H 4 
M0 4 . )0 4 .NH 2< crystallizing in yellowish-white needles. Gaultheria oil is iso- 
meric with anisic acid (see page 491), and yields by distillation at a high tem- 
perature with anhydrous lime and baryta, anisol C 14 H 8 2 , the same volatile 
oily liquid which is obtained from anisic acid by a similar process. 

Oil of valerian. — The oil obtained by distilling valerian-root with water 
has usually a viscid consistence, a yellowish colour, and a powerful and dis- 
agreeable odour. It consists of at least three principles, namely, valeric acid, 
borneene (see camphor), a light volatile liquid hydrocarbon, much resembling 
and isomeric with oil of turpentin, and valerol, a neutral oily body, much 
less volatile than the preceding, of feeble odour, and convertible by oxidizing 
agents into valeric acid. It contains C 12 H, O 2 . Borneene, under certain 
circumstances not well understood, assimilates the elements of water and 
yields the solid camphor of Borneo, or borneol. 

Camphor. — Common camphor yields a good example of a concrete essen- 
tial oil ; it is obtained by distilling with water the wood of the Laurus cam- 
phora. When pure, it forms a solid, white, crystalline, and translucent 
mass, tough, and difficult to powder, and having a powerful and very fami- 
liar odour. It melts when gently heated, and boils, distilling unchanged at 
a high temperature. It slowly sublimes at the temperature of the air, and 
often forms beautiful crystals on the sides of bottles or jars containing it 
exposed to the light. Camphor is very sparingly soluble in water, but readily 
soluble in alcohol, ether, and strong acetic acid. It contains C 10 H g O, or 

^20^16^2* 

By the action of nitric acid aided by heat, camphor is gradually oxidized 
and dissolved with production of camphoric acid ; this substance forms small 
colourless needles or plates, of acid and bitter taste, sparingly soluble in 
cold water, and containing Ci H 7 O 3 ,HO. It melts when heated, and yields 
by distillation a colourless, crystalline, neutral substance, containing C 10 H 7 
3 , improperly termed anhydrous camphoric acid. 

When camphorate of lime is submitted to distillation, it yields a volatile 
oil containing oxygen, in its formation and constitution similar to acetone 
(page 376) or benzophenone (page 398). This substance, phorone, contains 
C 9 H 7 or C 18 H 14 2 . By the action of anhydrous phosphoric acid it loses 
water and furnishes the hydrocarbon cumol, C 18 H 12 (see page 403). 

When camphor in vapour is passed over a mixture of hydrate of potassa 
and quicklime strongly heated in a tube, it is resolved without disengage- 
ment of gas into an acid body termed campholic acid, white, crystalline, and 
sparingly soluble in water, containing C 20 H ]7 O 3 ,HO. By distillation with 
anhydrous phosphoric acid, this acid gives a volatile hydrocarbon, campho- 
lene. Camphor itself, by a similar mode of treatment, yields a colourless 
volatile liquid, C 20 H 14 , formerly called eamphogcn, but since found to be iden- 
tical with the hydrocarbon, cymol, occurring in oil of cumin. 

The camphor of Borneo, procured from the Dryabalanops camphora, contains 
C 20 H, 8 O 2 ; it is accompanied by borneene, identical with that of the oil of 
valerian, and yields the same substance w r hen distilled with anhydrous phos- 
phoric acid. Nitric acid converts it into common camphor. 

The oils of peppermint, lavender, rosemary, orange-jlowers, rose-petals, and 
manv others, belong to the class of oxygenated essential oils. 

Essential Oils containing Sulphur. 

In the preparation of the sulphuretted volatile oils, distillatory vessels of 
copper, tin, or lead must be avoided, as those metals are attacked by the 
sulphur. In other respects their manufacture offers no peculiarities. 

Oil of mustard. — The most remarkable member of the class is the oil 
obtained by distillation from black mustard-seed. White mustard yields 



RESINS AND BALSAMS. 493 

sone. Both varieties give, by expression, a bland fat oil. The volatile oil 
doed not pre-exist in the seed, but is formed in the same manner as bitter- 
almond-oil, by the joint action of water and a peculiar coagulable albuminous 
matter upon a substance yet inperfectly known, present in the grain, and 
termed myronie acid. 

The distilled oil, when pure, is colourless ; it has a most powerful, pungent 
and suffocating smell, and a density of 1-015. Applied to the skin, it pro- 
duces almost instant vesication. It boils at 289° (145°-8C). Water dis- 
solves it in small quantity, and alcohol and ether very freely. The oil itself, 
at a high temperature, dissolves both sulphur and phosphorus, and deposits 
them in a crystalline form on cooling. It is oxidized with violence by nitric 
acid, and by aqua regia. Alkalis decompose it by the aid of heat, with pro- 
duction of ammonia, an alkaline sulphide, and a sulphocyanide. The re- 
markable compound with ammonia, thiosinnamine, has been already described 
(see page 406.) 

Mustard-oil gives by analysis C 8 H 5 NS 2 .' 

The oil of horse-radish, and that obtained from the roots of the Alliaria 
officinalis by distillation with water, are identical with the oil of black mus- 
tard-seed. 

Oil of garlic. — The crude oil procured by distilling the sliced bulbs with 
water is not a homogeneous product ; by the action of metallic potassium, 
however, renewed until it is no longer tarnished, a small portion of oxyge- 
netted oil which it contains may be decomposed and withdrawn, after which 
the sulphuretted compound may be obtained pure by re-distillation. In this 
state it forms a colourless liquid, lighter than water, of high refractive power, 
possessing in a high degree the peculiar odour of the plant, and capable of 
being distilled without decomposition. It contains C 6 H 5 S. Garlic-oil dis- 
solved in alcohol, and mixed with solutions of platinum, silver, and mercury, 
gives rise to crystalline compounds having the characters of double salts, 
containing the elements of the oil with the sulphur replaced by oxygen or 
chlorine. 

A curious and interesting relation exists between the oils of mustard and 
garlic : in both these substances, we may assume the existence of a radical 
C 6 H 5 , to which the name allyl has been given, when mustard-oil becomes the 
sulphocyanide, and garlic-oil the sulphide of allyl. 

Mustard-oil C g K 5 NS =C 6 H 5 C 2 NS 2 . Sulphocyanide of allyl. 
Garlic-oil C 6 H 5 S =C 6 H 5 S. Sulphide of allyl. 

This relation has been experimentally established. By mixing the oil 
with hydrate of soda and quicklime, and exposing the whole in an hermeti- 
cally-sealed tube to a temperature superior to that of boiling water, sulpho- 
cyanide of sodium is produced, together with an oily substance which is oxide 
of allyl, a substance chiefly known in combination, and which is the oxyge- 
netted constituent of crude garlic-oil. Again, if mustard-oil be treated in a 
similar manner with sulphide of potassium, sulphocyanide of potassium and 
garlic-oil are formed. On the other hand, when the compound of garlic-oil 
and chloride of mercury is gently heated with sulphocyanide of potassium, 
mustard-oil, with all its characteristic properties, is called into existence. 

The oils of assafoztida, and onions, contain sulphur, and consequently belong 
to the same series ; they have not yet been thoroughly examined. 

RESINS AXD BALSAMS. 

Common resin, or colophony, furnishes perhaps the best example of the 
class. The origin of this substance has been already described. It is a 
mixture of two distinct bodies, having acid properties ; called pink and sylvio 
42 



494 RESINS AND BALSAMS. 

acids, separable from each other by their difference of solubility in cold an 3 
somewhat dilute alcohol, the former being by far the more soluble of the 
two. Pure sylvic acid crystallizes in small, colourless, rhombic prisms, inso- 
luble in water, soluble in hot, strong alcohol, in volatile oils, and in ether. 
It melts when heated, but cannot be distilled without decomposition. The 
properties of pinic acid are very similar. Both have the same composition, 
viz., C 20 Hi 5 O 2 . A third resin-acid, also isomeric with the preceding, the 
pimaric, has been found in the turpentin of the Pinus maritima of Bordeaux. 

Lac is a very valuable resin, much harder than colophony, and easily so- 
luble in alcohol ; three varieties are known in commerce, viz., stick-lac, seed- 
lac, and shellac. It is used in varnishes, and in the manufacture of hats, and 
very largely in the preparation of sealing-wax, of which it forms the chief 
ingredient. Crude lac contains a red dye which is partly soluble in water. 
Lac dissolves in considerable quantity in a hot solution of borax ; Indian ink, 
rubbed up with this liquid, forms a most excellent label-ink for the laboratory, 
as it is unaffected by acid vapours, and, when once dry, becomes nearly in- 
soluble in water. 

Mastic, Dammar-resin, and sandarac are resins largely used by the varnish- 
maker. Dragon's-blood is a resin of a deep red colour. Copal is also a very 
valuable substance ; it differs from the other resins, in being with difficulty 
dissolved by alcohol and essential oils. It is miscible, however, in the melted 
state with oils, and is thus made into varnish. Amber appears to be a fossil 
resin ; it is found accompanying brown-coal or lignite. 

Caoutchouc. — This curious, and now most useful substance, is the produce 
of several trees of tropical countries, which yield a milky juice, hardened by 
exposure to the air. In a pure state, it is nearly white, the dark colour of 
commercial caoutchouc being due to the effects of smoke and other impuri- 
ties. Its physical characters are well known. It is softened, but not dis- 
solved by boiling water; it is also insoluble in alcohol. In pure ether, 
rectified native naphtha, and coal-oil, it dissolves, and is left unchanged on 
the evaporation of the solvent. Oil of turpentin also dissolves it, forming 
a viscid, adhesive mass, which dries very imperfectly. At a temperature a 
little above the boiling-point of water caoutchouc melts, but never afterwards 
returns to its former elastic state. Few chemical agents affect this substance ; 
hence its great practical use, in chemical investigations, for connecting ap- 
paratus, &c. Analysis shows it to contain nothing but carbon and hydrogen. 

By destructive distillation caoutchouc yields a large quantity of thin vola- 
tile oily liquid, of naphtha-like odour, to which the name caoutchoucin has 
been applied. This is probably a mixture of several hydrocarbons, scarcely 
to be separated from each other by distillation or otherwise. It dissolves 
caoutchouc with facility. 

A substance much resembling caoutchouc in certain respects, and of simi- 
lar origin, has lately been introduced under the name of gutta percha. It is 
capable of many useful applications in the laboratory. 

Most of the resins, when exposed to destructive distillation, yield liquid, 
oily pyro-products, usually carbides of hydrogen, which have been studied 
with partial success. Great difficulties occur in these investigations ; the 
task of separating from each other, and isolating bodies which scarcely differ 
but in their boiling-points, is exceedingly troublesome. 

Balsams are also, as before hinted, natural mixtures of resins with volatile 
oils. These differ very greatly in consistence, some being quite fluid, others 
solid and brittle. By keeping, the softer kinds often become hard. Balsams 
may be conveniently divided into two classes, viz., those which, like common 
and Venice turpentin, Canada balsam, copaiba balsam, &c, are merely natural 
varnishes, or solutions of resins in volatile oils, and those which contain bee- 



RESINS AND BALSAMS. 495 

«oic or cinnamic acid in addition, as Peru and Tolu balsams, and the solid 
resinous benzoin commonly called gum-benzoin. 

Tolu-balsam, by distillation with water, yields three products ; namely, 
benzoic acid, cinnamein, and tolene, a volatile colourless hydrocarbon, boiling at 
338° (170°C), and containing C 10 H 8 . The balsam freed in this manner from 
essential oils, exposed to destructive distillation, yields in succession a vis- 
cous liquid which crystallizes in the receiver, and a thin liquid heavier than 
water ; carbonic acid and carbonic oxide are largely evolved, and the retort 
is afterwards found to contain a residue of charcoal. The solid product is 
chiefly a mixture of benzoic and cinnamic acids ; the volatile oil contains at 
least two substances differing in their boiling-points, and easily separated, 
namely, toluol (benzoene), which has been mentioned already as a derivative 
of toluylic acid (see page 403), and an oily liquid heavier than water, of high 
boiling-point, and having the composition and characters of benzoic ether. 

Toluol is a thin, colourless liquid, insoluble in water, sparingly soluble in 
alcohol, more freely in ether; it has the odour of benzol ; its sp. gr. is 0-870, 
and it boils at 226° (107°-5C). The density of its vapour is 3-26, and its for- 
mula C, 4 H g . It combines with fuming sulphuric acid to the compound sul- 
photuolic acid: with nitric acid it yields two products, nitrotoluol, C 14 H 7 N0 4 , 
and binitrotoluol, C 14 H 6 i\ T 2 8 . The former is fluid, heavier than water, and 
bears a great resemblance in odour and other properties to nitrobenzol ; the 
latter is a solid, fusible, crystallizable substance. The conversion of nitro- 
toluol into the organic base toluidine, has been already described (see page 
462). 

Liquid siorax distilled with water, holding in solution a little carbonate of 
soda, yields a small and variable quantity of volatile oil, not homogeneous, 
but from which, by careful distillation, a liquid volatile hydrocarbon, termed 
styrol, can be extracted in a state of purity. It is thin and colourless, of 
powerful aromatic odour, refuses to solidify when cooled to 0° ( — 17°-8C), 
and boils at 293° (145° -C). Its sp. gr. is 0-924; it is nearly insoluble in 
water, but mixes freely with alcohol and ether. Styrol contains C ]6 H g , and 
is consequently isomeric with benzol. This substance is also produced by 
the action of lime or baryta upon cinnamic acid (see page 408), whence it is 
more appropriately termed cinnamol. 

When a portion of styrol is hermetically sealed in a glass tube, and then 
exposed for half an hour to a temperature approaching 400° (204°-5C) by 
means of an oil-bath, it undergoes a most remarkable change, becoming con- 
verted into a solid, transparent, glassy, fusible substance, called metastyrol, 
isomeric, as might be expected, with styrol itself. The same change is 
slowly produced by the influence of sunshine. A portion of metastyrol is 
always formed when styrol is distilled in a retort without water. Metastyrol 
is again convertible by distillation at a high temperature into liquid styrol. 

Certain of the products of the distillation of dragon's-blood appear to be 
identical with these bodies. 



496 COMPONENTS OF THE ANIMAL BODY, 



SECTION VIII. 
COMPONENTS OF THE ANIMAL BODY. 



Albuminous principles, albumin. — The fluid portion of blood -which 
has been some time drawn from the living body, and the white of eggs, con- 
tain this substance as their chief and characteristic ingredient. In the 
purest form in which albumin has yet been obtained it is insoluble, or nearly 
so, in water. If clear serum of blood, or white of egg mixed with a little 
water and filtered, be exactly neutralized by acetic acid, and then largely 
diluted with pure cold water, a copious flocculent precipitate falls, which 
may be collected on a filter, and washed. In this state it is nearly colour- 
less, inodorous, and tasteless ; it dissolves with facility in water containing 
an exceedingly small quantity of caustic alkali, and gives a solution which 
has all the characters of the original liquid. When dried by gentle heat, 
it shrinks to a very small bulk, and becomes a translucent, horny mass, 
which softens in water, and exhales when exposed to heat the usual ammo- 
niacal products of animal matter, leaving a bulky coal, very difficult of com- 
bustion. When white of egg is thinly spread upon a plate and exposed to 
evaporation in a warm place, it dries up to a pale yellow, brilliant, gum-like 
substance, destitute of all traces of crystalline structure. In this state it 
may be preserved unchanged for any length of time, the presence of water 
being in all cases necessary to putrefactive decomposition. The dried white 
of egg may also be exposed to a heat of 212° (100°C) without alteration 
of properties. When put into slightly warm water, it softens, and at length 
in great measure dissolves. When reduced to fine powder and washed upon 
a filter with cold water, common salt, sulphate, phosphate, and carbonate 
of soda are dissolved out, together with mere traces of organic matter, while 
a soft swollen mass remains upon the filter, which has all the characters of 
pure albumin obtained by precipitation. When dried and incinerated, this 
leaves nothing but a little phosphate of lime. 

It thus appears likely that albumin is really an insoluble substance, and 
that its soluble state in the animal system is due to the presence of a little 
alkali. 

When natural albumin is exposed to heat it solidifies, or coagulates. The 
temperature required for this purpose varies with the state of dilution. If 
the quantity of albumin be so great that the liquid has a slimy aspect, a 
heat of 145° or 150° (62°-5 or 69°-5C) suffices, and the whole becomes solid, 
white, and opaque ; in a very dilute condition, boiling is required, and the 
albumin then separates in light, finely divided flocks. Thus changed by 
heat, albumin becomes quite insoluble in water : it dries up to a yellow, 
transparent, horny substance, which when macerated in water resumes its 
former whiteness and opacity. In dilute caustic alkali it dissolves with 
facility, and in this respect resembles the insoluble albumin just described; 
it differs, however, from the latter in not being soluble in a strong solution 



COMPONENTS OF THE ANIMAL BODY. 497 

of nitrate of potassa, -which dissolves with great ease that substance. The 
oply chemical change that can be traced in the act of coagulation is the loss 
of alkali and soluble salts, which are removed by the hot water. 

A solution of ordinaiy albumin gives precipitates with excess of sulphuric, 
hydrochloric, nitric, and meta-phosphoric acids ; but neither with acetic nor 
with common or tribasic phosphoric acid. These precipitates, which, though 
soluble in water, are insoluble in an excess of dilute acid, are looked upon 
as direct compounds of albumin with the acids in question. Most of the 
metallic salts, as those of copper, lead, mercury, &c., form insoluble com 
pounds with albumin, and give precipitates with its solution ; hence the 
value of white of egg as an antidote in cases of poisoning with corrosive 
sublimate. Alcohol, added in large quantity, precipitates albumin. Tannic 
acid, or infusion of galls, gives with it a copious precipitate. By these cha- 
racters the presence of albumin may be readily discovered, -and its identi- 
fication effected ; a very feebly alkaline liquid, if containing albumin, coagu- 
lates by heat, becomes turbid on the addition of nitric acid, and previously 
acidulated by acetic acid, gives a precipitate with solution of corrosive 
sublimate. It must be remembered, that a considerable quantity of alkali, 
and very minute quantities of the mineral acids, prevent coagulation by heat, 
and the addition of acetic acid, indispensable to the mercury-test, produces 
the same effect. 

The chemical composition of albumin has been carefully studied ; it con- 
tains in 100 parts : — 

Carbon 53-5 

Hydrogen 70 

Nitrogen 15-5 

Oxygen 220 

Phosphorus 0-4 

Sulphur 1-6 

100-0 

The existence of unoxidized sulphur in albumin is easily shown ; a boiled 
egg blackens a silver spoon from a trace of alkaline sulphide formed or sepa- 
rated during the coagulation; and a solution of albumin in excess of caustic 
potassa, mixed with a little acetate of lead, gives on boiling a black preci- 
pitate containing sulphide of lead. 

Fibrin. — This substance is found in solution in the blood. It is procured 
by washing the coagulum of blood in a cloth until all the soluble portions 
are removed, or by agitating fresh blood with a bundle of twigs, when the 
fibrin attaches itself to the latter, and is easily removed and cleansed by 
repeated washing with cold water. The only impurity then remaining is a 
small quantity of fat, which can be extracted by ether. In the fresh state 
fibrin forms long, white, elastic filaments ; it is quite tasteless, and inso- 
luble in both hot and cold water. By long-continued boiling it is partly 
dissolved. When dried in vacuo, or at a gentle heat, it loses about 80 per 
cent, of water, and becomes translucent and horny ; in this state it closely 
resembles coagulated albumin. Fresh fibrin wetted with concentrated acetic 
acid, forms, after some hours, a transparent jelly, which slowly dissolves 
in pure water ; put into a very dilute caustic alkali, fibrin dissolves com- 
pletely, and the solution exhibits many of the characters of albumin. Phos- 
phoric acid produces a similar effect. Boiled with strong hydrochloric acid 
for severalhours, fibrin is converted into a mixture of leucine (see page 477) 
and tyrosine (see page 500). 

The fibrin of arterial and venous blood is not absolutely the same ; wnen 
the venous fibrin of human blood is triturated in a mortar with 1 h times its 
42* 



498 COMPONENTS OF THE ANIMAL BODY. 

weight of water and J of its weight of nitrate of potassa, and the mixture is 
left 24 hours or more at a temperature of 100°— 120° (37°-7— 48°-8C), it 
"becomes gelatinous, slimy, and eventually entirely liquid; in this condition 
it exhibits all the properties of a solution of albumin which has been neu- 
tralized by acetic acid. It coagulates by heat, it is precipitated by alcohol, 
corrosive sublimate, &c, and when largely diluted it deposits a flocculent 
substance, not to be distinguished from insoluble albumin. 1 With arterial 
fibrin, on the contrary, no such liquefaction happens, and even the fibrin of 
venous blood, when long exposed to the air, or to oxygen gas, loses the pro- 
perty in question. 

In the soluble state, fibrin is in great measure unknown ; when withdrawn 
from the influence of life, it coagulates spontaneously after a certain interval, 
giving rise to the production of the clot which appears in blood left to itself, 
and which consists of a kind of fine net-work of fibres, swollen with liquid 
serum, and inclosing the little red colouring particles of the blood, hereafter 
to be described. 

Mr. Mulder found dried fibrin, carefully freed from fat, to be composed as 
follows : — 

Carbon 52-7 

Hydrogen 6-9 

Nitrogen 15-4 

Oxygen 23-5 

Phosphorus 0-3 

Sulphur 1-2 

100-0 

The ash, or incombustible portion of fibrin, varying from 0*7 to 2-5 per 
cent, consists chiefly of the phosphate of lime. 

Casein. — This is the characteristic azotized component of milk, and the 
basis of the various preparations termed cheese ; it is not known to occur in 
any other secretion. Casein very closely resembles albumin in many par- 
ticulars, and may even be occasionally confounded with it. Like that sub- 
stance, it is insoluble in water when in a state of purity, and only assumes 
the soluble condition in the presence of free alkali, of which, however, a very 
small quantity suffices for the purpose. To prepare casein, fresh milk is 
gently warmed with dilute sulphuric acid, the coagulum produced well washed 
with water, dissolved in a dilute solution of carbonate of soda, and placed in 
a warm situation to allow the fat or butter to separate from the watery 
liquid. The latter is then removed by a siphon, and re-precipitated by sul- 
phuric acid. These precipitations and re-solutions in dilute alkali are several 
times repeated. Lastly, the insoluble casein is well washed with boiling 
water, and treated with ether to remove the last traces of fat. In this state 
it is a white curdy substance, not sensibly soluble in pure water or in alcohol, 
but dissolved with great ease by water containing a little caustic or carbo- 
nated alkali. It is also soluble to a certain extent in dilute acids, from 
which it may be precipitated by cautious neutralization. The precipitate 
formed by an acid in a strong solution of casein contains acid in combination, 
which, however, may be entirely removed by washing. In the moist state 
casein reddens litmus-paper, and masks the reaction of an alkaline car- 
bonate When incinerated, it leaves about 03 per cent, of incombustible 
matter. 

A solution of casein in very dilute alkali, as in milk, does not coagulate 
en boiling. On evaporation the surface becomes covered by a skin,. and the 

1 Liebig, Ilaudworterbuch der Ckeniie, i. S81. 



COMPONENTS OF THE ANIMAL BODY. 499 

■whole eventually dries up to a translucent mass. Acetic acid precipitates 
casein, which is a distinctive character between that substance and albumin. 

By fusion with hydrate of potassa casein yields valerianic and butyric 
acids, besides other products. 

The most striking property of casein is its coagulability by certain animal 
membranes. This is well seen in the process of cheese-making, in the pre- 
paration of the curd. A piece of the stomach of the calf, with its mucous 
membrane, is slightly washed, put into a large quantity of milk, and the 
whole slowly heated to about 122° (50°C). In a short time after this tem- 
perature has been attained, the milk is observed to separate into a solid, 
white coagulum, or mass of curd, and into a yellowish, translucent liquid 
called whey. The curd contains all the casein of the milk, much of the fat, 
aud much of the inorganic matter ; the whey retains the milk-sugar and the 
soluble salts. It is just possible that this mysterious change may be really 
due to the formation of a little lactic acid from the milk-sugar, under the 
joint influence of a slowly decomposing membrane and the elevated tempe- 
rature, and that this acid may be sufficient in quantity to withdraw the 
alkali which holds the casein in solution, and thus occasion its precipitation 
in the insoluble state. The loss of weight the membrane itself suffers in thia 
operation is very small ; it has been found not to exceed y^ - part. 

Casein has been carefully analysed by Mulder ; it contains in 100 parts — 

Carbon 53-83 

Hydrogen 7-15 

Nitrogen 15-65 

Oxygen "> 9q -q7 

Sulphur) ' 

100-00 

When precipitated by acetic acid and washed with alcohol and ether it 
contains about 1 per cent, of sulphur. When not treated with acid it con- 
tains about 6 per cent, of phosphate of lime. 

A comparison of the composition of these three bodies described is very 
remarkable, as it shows that they are very closely related in composition. 
The fibrin contains rather a larger quantity of oxygen than the albumin, and 
the casein contains no phosphorus. As, however, it is very doubtful whether 
these substances have been obtained in an unmixed and pure state no for- 
mulae can be given. 

Protein. — Mulder observed that when albumin, fibrin, or casein was dis- 
solved in a moderately strong solution of caustic alkali, and digested at 140° 
(60° -C), or thereabouts, in an open vessel until the liquid ceased to blacken 
with a salt of lead, and then filtered, and mixed with a slight excess of 
acetic acid, a copious, snow-white flocculent precipitate fell, and a faint odour 
of sulphuretted hydrogen was evolved. The new substance he called pro- 
tein. 1 He stated that it was free from sulphur and phosphorus, and that it 
was by the combination of different quantities of these elements with pro- 
tein, that albumin, fibrin, and casein, were produced, the protein pre-existing 
in each of these substances. It is, however, now admitted, that neither by 
the above-mentioned treatment, nor in any way, can a substance free from 
sulphur be obtained, and the protein must therefore be considered as one of 
the first products of the decomposition of albumin, fibrin, and casein, bv 
moderately strong caustic alkali. 

When albumin, fibrin, or casein, are boiled in strong solution of potassa 

1 So called from rpwrstlw, I take the fir st place; in allusion to its alleged important relations 
to the albuminous principles. 



500 COMPONENTS OP THE ANIMAL BODY. 

as long as ammoniacal vapours are given off, the liquid then neutralized 
with sulphuric acid, evaporated to dryness, and the product exhausted by 
boiling alcohol, three compounds are dissolved out, viz., a soluble, brown 
extract-like substance, erythroprotide ; a soluble straw-yellow substance, pro- 
tide, and a curious crystallizable principle, leucine, which forms small coloui'- 
less scales, destitute of taste and odour, soluble in water and alcohol, and in 
concentrated sulphuric acid without decomposition. When heated, it sub- 
limes unchanged. Leucine contains C l2 H ]3 N0 4 , (see page 501). 

Binoxide and Terozide of Protein. — These names were given by Mulder to 
products of the long-continued action of boiling water upon fibrin in contact 
with air; they are said to be the chief ingredients also of the huffy coat of 
blood in a state of inflammation, being produced at the expense of the 
fibrin. 1 They cannot be obtained free from sulphur. Binoxide of protein is 
quite insoluble in water, but dissolves in dilute acids ; when dry, it is dark 
coloured. The soluble part of the fibrin-decoction contains terozide of protein, 
which somewhat resembles, and has been confounded with, gelatin. It is 
freely soluble in boiling water, and in dilute alkalis. Coagulated albumin 
is slowly dissolved by boiling water, and said to be converted into this sub- 
stance. The solution in cold water gives a precipitate with nitric acid which 
is re-dissolved on the application of heat, and re-precipitated when cooled. 
A substance closely resembling this in its reactions and composition has been 
found in the urine of a patient suffering from molleiies ossium. 2 

When chlorine gas is passed to saturation into a solution of ordinary albu- 
min, or either fibrin or casein dissolved in ammonia, a white, flocculent, in- 
soluble substance falls, which, when washed and dried, becomes a soft yel- 
lowish powder. This is supposed to be a compound of chlorous acid and 
protein ; when digested with ammonia, it yields sal-ammoniac and teroxide 
of protein. 

Gelatin and chondrin. — Animal membranes, skin, tendons, and even 
bones, dissolve in water at a high temperature more or less completely, but 
with very different degrees of facility, giving solutions which on cooling ac- 
quire a soft-solid, tremulous consistence. The substance so procured is 
termed gelatin ; it does not pre-exist in the animal system, but is generated 
from the membranous tissue by the action of hot water. The jelly of calves' ; 
feet, and common size and glue, are familiar examples of gelatin in different 
conditions of purity. Isinglass, the dried swimming-bladder of the stur- 
geoD, dissolves in water merely warm, and yields a beautifully pure gelatin. 
In this state it is white and opalescent, or translucent, quite insipid and in- 
odorous, insoluble in cold water, but readily dissolving by a slight elevation 
of temperature. Cut into slices and exposed to a current of dry air, it 
shrinks prodigiously in volume, and becomes a transparent, glassy, brittle 
mass, which is soluble in warm water, but insoluble in alcohol and ether. 
Exposed to destructive distillation, it gives a large quantity of ammonia, in- 
flammable gases, nauseous empyreumatic oil, and leaves a bulky charcoal 
containing nitrogen. In a dry state, gelatin may be kept indefinitely ; in 
contact with water, it putrefies. Long-continued boiling gradually alters it, 
and the solution loses the power of forming a jelly on cooling. 1 part of 
dry gelatin or isinglass dissolved in 100 parts of water solidifies on cooling. 

An aqueous solution of gelatin is precipitated by alcohol, which withdraws 
the water ; corrosive sublimate in excess gives a white flocculent pi-ecipitate, 
and the same happens with solution of nitrate of the sub- and protoxide of 
mercury ; neither alum, acetate, nor basic acetate of lead affect a solution 
<»f gelatin. With tannic acid or infusion of galls, gelatin gives a copious, 

1 Mulclpr, Aunalen der Cbemie uud Pharmacic, xlvii. 323. 
3 See Pbilo?cphical Trans. ISIS. 



COMPONENTS OF THE ANIMAL BODY. 501 

whitish, curdy precipitate, which coheres on stirring to an elastic mass, 
quite insoluble in water, and incapable of putrefaction. 

Chlorine passed into a solution of gelatin occasions a dense white precipi- 
tate of chlorite of gelatin, which envelopes each gas-bubble, and ultimately 
forms a tough, elastic, pearly mass, somewhat resembling fibrin. Boiling 
with strong alkalis converts gelatin, with evolution of ammonia, into leucine, 
and a sweet crystallizable principle, gelatin- sugar, or glycocoll, or better, 
glycocine containing C 4 H 5 N0 4 . This remarkable substance was first formed 
by the action of cold concentrated sulphuric acid upon gelatin, and has 
lately been obtained by the action of acids upon hippuric acid, which is 
thereby resolved into benzoic acid and glycocine (see page 402). It forms 
colourless crystals, freely soluble in water, and unites to crystallizable com- 
pounds with a great number of bodies, acids, bases and salts. Glycocine, 
when treated with nitrous acid, yields an acid homologous to lactic acid (sea 
page 402), to which the name of glycolic acid has been given. 

C 4 H 5 N0 4 + N0 3 = C 4 H 4 6 -f 2N-f HO 

Glycocine. Glycolic acid. 

This substance, which is but imperfectly studied, appears to be present like- 
wise in the mother-liquor from which the fulminate of silver has been 
deposited. There exists a remarkable relation between glycocine, alanine, 
and leucine, two substances which have been previously described (pages 
467 and 500). These three bodies are homologous, as will be seen from the 
following formulas : — 

Glycocine C 4 H 5 N0 4 

Alanine C 6 H 7 N0 4 

Leucine C 12 H ]3 N0 4 . 

The deportments of these three substances with nitrous acid is perfectly 
alike. Leucine, according to M. Strecker, yields a new acid C !2 H ]2 6 homo- 
logous to glycolic and lactic acids, which has not yet been perfectly ex- 
amined. 

When a dilute solution of gelatin is distilled with a mixture of bichromate 
of potassa and sulphuric acid, it yields a number of extraordinary products, 
as acetic, valerianic, benzoic, and hydrocyanic acids, and two volatile oily 
principles termed valeronitrile and valeracetonitrile. The former is a thin 
colourless liquid, of aromatic odour, like that of hydride of salicyl ; it is 
lighter than water, boils at 257° (125°C), and contains C 10 H 9 N. The latter 
much resembles the first, but boils at 158° (70°C), and contains CggH^NgOg. 
Alkalis convert valeronitrile into valerianic acid and ammonia, and valera- 
cetonitrile into valerianic and acetic acids and ammonia. It is very pro- 
bable that the latter compound is a mixture of acetonitrile and valeronitrile. 
Dry gelatin, subjected to analysis, has been found to contain in 100 
parts : — 

Carbon 50-05 

Hydrogen 6-47 

Nitrogen 1835 

Oxygen 25-13 

100-00 

From these numbers the formulas Ci 3 H 10 N 2 O 5 , and C 52 H 40 N 8 O 2& , have been 
deduced. 

The cartilage of the ribs and joints yields a gelatin differing in some re- 
spects from the preceding; it is called, by way of distinction, chondrin. 



502 COMPONENTS OF THE ANIMAL BODY. 

Acetate of lead and solution of alum precipitate this substance, which is 
not the case with common gelatin. To chondrin the formulae C 32 H 26 N 4 14 , 
and C 48 II 40 N 6 O 20 have been given. 

If a solution of gelatin, albumin, fibrin, casein, or probably any one of 
the more complex azotized animal principles, be mixed with solution of sul- 
phate of copper, and then a large excess of caustic potassa added, the 
greenish precipitate first formed is re-dissolved, and the liquid acquires a 
purple tint of indescribable magnificence and great intensity. 

Gelatin is largely employed as an article of food, as in soups, &c. ; but its 
value in this respect has been much overrated. In the useful arts, size and 
glue are consumed in great quantities. These are prepared from the clip- 
pings of hides, and other similar matters, inclosed in a net, and boiled with 
water in a large cauldron. The strained solution gelatinizes on cooling, and 
constitutes size. Glue is the same substance in a state of desiccation, the 
size being cut into slices and placed upon nettings, freely exposed to a cur- 
rent of air. Gelatin is extracted from bones with much greater difficulty . 
the best method of proceeding is said to be to inclose the bones, previously 
crushed, in strong metallic cylinders, and admit high-pressure steam, which 
attacks and dissolves the animal matter much more easily than boiling 
water ; or, to steep the bones in dilute hydrochloric acid, thereby removing 
the earthy phosphate, and then dissolve the soft and flexible residue by 
boiling. 

There is an important economical application of gelatin, or rather of the 
material which produces it, which deserves notice, viz., to the clarifying of 
wines and beer from the finely divided and suspended matter which often 
renders these liquors muddy and unsightly. When isinglass is digested in 
very dilute cold acetic acid, as sour wine or beer, it softens, swells, and 
assumes the aspect of a very light transparent jelly, which, although quite 
insoluble in the cold, may be readily mixed with a large quantity of watery 
liquid. Such a preparation, technically called finings, is sometimes used by 
brewers and wine-merchants for the purpose before-mentioned ; its action on 
the liquor with which it is mixed seems to be purely mechanical, the gela- 
tinous matter slowly subsiding to the bottom of the cask, and carrying with 
it the insoluble substance to which the turbidity was due. 

Kreatin and kreatinine. — Kreatin was first observed by Chevreul, and 
has lately been studied very carefully by Professor Liebig, who obtained it 
from the soup of boiled meat ; it is best prepared from the juice of raw flesh 
by the following process: — A large quantity of lean flesh is cut up into 
shreds, exhausted by successive portions of cold water, strained and pressed. 
The liquid, which has an acid reaction, is heated to coagulate albumin and 
colouring matter of blood, and passed through a cloth. It is then mixed 
with pure baryta-water as long as a precipitate appears, filtered from the 
deposit of phosphates, and evaporated in a water-bath to a syrupy state. 
After standing some days in a warm situation, the kreatin is gradually 
deposited in crystals, which are easily purified by re-solution in water and 
digestion with a little animal charcoal. 

When pure, kreatin forms colourless, brilliant, prismatic crystals, which 
become dull by loss of water at 212° (100°C). They dissolve readily in boil- 
ing water, sparingly in cold, and are but little soluble in alcohol. The 
aqueous solution has a weak bitter taste, followed by a somewhat acrid sen- 
sation. In an impure state the solution readily putrifies. Kreatin is a neu- 
tral body, not combining either with acids or alkalis. In the crystallized 
state it contains C 8 H 9 N 3 4 ,2HO. 

By the action of strong acids, kreatin is converted into Icrcatinine, a power- 
ful organic base, with separation of the elements of water. The new sub- 
stance forms colourless prismatic crystals, and is much more soluble in water 



COMPOSITION OF THE BLOOD. 503 

than kreatin ; it has a strong alkaline reaction, forms "with acids crystalli- 
zable salts, and contains C 8 H 7 N 3 2 . 

Kreatinine pre-exists to a small extent in the juice of flesh, together with 
lactic acid and other bodies yet imperfectly examined. It is also found in 
conjunction with kreatin in urine. 

When kreatin is long boiled with solution of caustic baryta, it is gradually 
resolved into urea, subsequently decomposed into carbonic acid and ammo- 
nia, and a new organic body of basic properties, sarcosine. The latter, when 
pure, forms colourless transparent plates, extremely soluble in water, 
sparingly soluble in alcohol, and insoluble in ether. When gently heated 
they melt and sublime without residue. Sarcosine forms with sulphuric acid 
a crystallizable salt, and contains C 6 H 7 N0 4 , being isomeric with lactamide, 
alanine, and urethane. 

The mother-liquid from flesh from which the kreatine has been deposited 
contains, among other things, a new acid, the inosinic, the aqueous solution 
of which refuses to crystallize. It has a strong acid reaction, and is preci- 
pitated in a white amorphous condition by alcohol. It probably contains 
CjoHgNjjO^HO. 1 Recently, moreover, a kind of sugar, which however does 
not ferment, has been found in the juice of flesh. It was discovered by 
Scherer, who calls it inosite, and gives the composition C 12 H 12 O l2 -4-4HO, 
This substance crystallizes in beautiful crystals. 

Composition of the blood ; respiration. — The blood is the general cir- 
culating fluid of the animal body, the source of all nutriment and growth, 
and the general material from which all the secretions, however much they 
may differ in properties and composition, are derived. Food or nourish- 
ment from without can only be made available by being first converted into 
blood. It serves also the scarcely less important office of removing and 
carrying off principles from the body which are hurtful, or no longer re- 
quired. 

In all vertebrated animals the blood has a red colour, and probably in all 
cases a temperature above that of the medium in which the creature lives. 
In the mammalia this is very apparent, and in the birds still more so. The 
heat of the blood is directly connected with the degree of activity of the 
respiratory process. In man the temperature of the blood seldom varies 
much from 98° (86°-6C), when in a state of health, even under great vicissi- 
tudes of climate; in birds it is sometimes as high as 109° (42° -8C). To 
these two highest classes of the animal kingdom, the mammifers and the 
birds, the observations about to be made are intended especially to apply. 

In every creature of this description two kinds of blood are met with, 
which differ very considerably in their appearance, viz., that contained in 
the left side of the heart and in the arteries generally, and that contained 
in the right side of the heart and in the veins ; the former, or arterial blood, 
has a bright red colour, the latter, the venous blood, is blackish purple. 
Farther, the conversion of the dark into the florid blood may be traced to 
what takes place during its exposure to the air in the lungs, and the oppo- 
site change, to what takes place in the capillaries of the general vascular 
system, or the minute tubes or passages, distributed in countless numbers 
throughout the whole body, which connect the extremities of the arteries 
and veins. When compared together, little difference of properties or com- 
position can be found in the two kinds of blood ; the fibrin varies a little, 
that from venous blood being, as already mentioned, soluble in a solution of 
nitrate of potassa, which is not the case with arterial fibrin. It is very 
prone, besides, to absorb oxygen, and to become in all probability partly- 
changed to the substance called binoxide of protein, which no doubt exists 

1 Liebig, Chemistry of Food. 




504 COMPOSITION OF THE BLOOD.' 

in the fibrin of arterial blood. The only other notable point of difference is 
in the gaseous matter the blood holds in solution, carbonic acid predomina- 
ting in the venous, and free oxygen in the arterial variety. 

In its ordinary state the blood has a slimy feel, a density varying from 
1-053 to 1-057, and a decidedly alkaline reaction ; it has a saline and disa- 
greeable taste, and, when quite recent, a peculiar odour or halitus, which 
almost immediately disappears. An odour may, however, afterwards be de- 
veloped by an addition of sulphuric acid, which is by some considered char- 
acteristic of the animal from which the blood was obtained. 

The coagulation of blood in repose has been already noticed, and its cause 
traced to the spontaneous solidification of the fibrin : the effect is best seen 
when the blood is received into a shallow vessel, and left to itself some time. 
No evolution of gas or absorption of oxygen takes place in this process. By 
strong agitation coagulation may be prevented ; the fibrin in this case sepa- 
rates in cohering filaments. 

To the naked eye the blood appears a homogeneous fluid, but it is not so in 
reality. When examined by a good microscope, it 
Fi S- 174 - is seen to consist of a transparent and nearly 

(3) colourless liquid, in which float about a countless 

^~ © multitude of little round red bodies, to which the 

© © © f^ colour is due ; these are the blood-discs or blood- 

fi^(8) corpuscles of microscopic observers. Fig. 174. 

© O They are accompanied by colourless globules, 
/=f5> fewer and larger, the white corpuscles of the blood. 

(gp) ^~^ <&&) The blood-discs are found to present different 

/pv ® ^ (Oj©^ appearances in the blood of different animals : in 
Q q © ^ ©@ the mammifers they look like round red or yel- 
.-.Q (SX, © lowish discs, thin when compared with their diam- 

© © \ri^ eter, being flattened or depressed on opposite 

(qWa©)© ® sides. In birds, lizards, frogs, and fish, the cor- 

^^^ ® © ©) puscles are elliptical. In magnitude, they seem 

© © to be pretty constant in all the members of a spe- 

cies, but differ with the genus and order. In man 
they are very small, varying from ^l^ tOgJ^-g- of an inch in breadth, while in 
the frog the long diameter of the ellipse measures at least four times as much. 
The corpuscles consist of an envelope containing a fluid in which the red 
colouring-matter of the blood is dissolved. 

The coagulation of blood effects a kind of natural proximate analysis ; the 
clear, pale serum, or fluid part, is an alkaline solution of albumin, containing 
various soluble salts ; the clot is a mechanical mixture of fibrin and blood 
globules, swollen and distended with serum, of which it absorbs a large but 
variable quantity. 

When the coagulum of blood is placed upon bibulous paper, and drained 
as much as possible from the fluid portion, and then put into water, the en- 
velope, which consists of globulin, dissolves and sets free the colouring matter, 
forming a magnificent crimson solution, which has many of the characters 
of a dye-stuff. It contains albumin and globulin, and coagulates by heat 
and by the addition of alcohol ; this albumin and globulin cannot be sepa- 
rated, and attempts to isolate the hemalosin or red pigment have consequently 
failed. From its extreme susceptibility of change, it is not known in a state 
of purity. The above watery solution, exposed with extensive surface in a 
warm place, dries up to a dark red, brittle mass, Avhich is again soluble in 
water. After coagulation it becomes quite insoluble, but dissolves like albumin 
in caustic alkalis. Carbonic and sulphurous acids blacken the red solution ; 
oxygeu, or atmospheric air, heightens its colour; protoxide of nitrogen 



COMPOSITION OF THE BLOOD. 505 

renders it purple ; -while sulphuretted hydrogen, or an alkaline sulphide, 
changes it to a dirty greenish black. 

Hematosin differs from the other animal principles in containing as an es- 
sential ingredient a remarkable substance not found elsewhere in the animal 
system, viz., the oxide of the metal iron. If a little of the dried clot of blood 
be calcined in a crucible and digested with dilute hydrochloric acid, a solution 
will be obtained rich in oxide of iron ; or if the solution of colouring matter 
just referred to be treated with excess of chlorine gas, the yellow liquid 
separated from the greyish coagulum formed will be found to give in a striking 
manner the well-known reactions of the sesquioxide of iron. There is little 
doubt, either about the condition of the metal'; sesquioxide of iron is with- 
drawn from the dry clot by the cautious addition of sulphuric acid, and 
without much alteration of the colour of the mass. 1 It is well known that 
certain organic matters, as tartaric aojd, prevent the precipitation of sesqui- 
oxide of iron by alkalis, and its recognition by ferrocyanide of potassium, 
and it is very likely that the blood may contain a substance or substances 
capable of doing the same. 

Hematosin, necessarily in a modified state, contains, according to Mulder, 
in 100 parts : — 

Carbon 65-3 

Hydrogen 5-4 

Nitrogen 10-4 

Oxygen 11-9 

Iron '. 7-0 



100-0 



The following table represents the composition of healthy human blood as 
whole ; it is on the authority of M. Lecanu. 2 

CD (2-) 

Water 780-15 785-58 

Fibrin 2-10 3-57 

Albumin 65-09 6941 

Colouring matter 133-00 119-63 

Crystallizable fat 2-43 4-30 

Fluid fat 1-31 2-27 

Extractive matter of uncertain nature, soluble in ) .. _q .. q9 

both water and alcohol / ' 

Albumin in combination with soda 1-26 2-01 

Chlorides of sodium and potassium ; carbonates, ") 0.07 ".QA 

phosphates, and sulphates of potassa and soda... j 

Carbonates of lime and magnesia; phosphates of) 9. in 1.J9 

lime, magnesia, and iron; sesquioxide of iron... J 

Loss : 2-40 2-59 



1000-00 1000-00 

In healthy individuals of different sexes these proportions are found to vary 
slightly, the fibrin and colouring matter being usually more abundant in the 
male than in the female ; in disease, variations of a far wider extent are often 
apparent. 

It appears singular that the red corpuscles, which are so easily dissolved 
by water, should remain uninjured in the fluid portion of the blood. This 
eeems partly due to the presence of saline matter, and partly to that of albu-« 

1 Liet>i.2, Handwurterbuch, i. 585. * Ann. Chim. et de Phys. xlviii. 320 

43 



506 FTJNC TI ON OF RESPIRATION. 

min, the corpuscles being alike insoluble in a strong solution of salt and in a 
highly albuminous liquid. In the blood the limit of dilution within -which the 
corpuscles retain their integrity appears to be nearly reached, for when 
•water is added they immediately become attacked. 

Closely connected "with the subject of the composition of the blood are those 
of respiration, and of the production of animal heat. 

The simplest view that can be taken of a respiratory organ in an air-breath- 
ing animal, is that of a little membranous bag, saturated with moisture, and 
containing air, over the surface of which meanders a minute blood-vessel, 
whose contents, during their passage, are thus subjected to the chemical 
action of the air through the substance of the membranes, and in virtue of 
the solubility of the gaseous matter itself in the water with which the mem- 
branes are imbued. In some of the lower classes of animals, where respira- 
tion is sluggish and inactive, these air-cells are few and large ; but in the 
higher kinds they are minute, and greatty multiplied in number, in order to 
gain extent of surface, each communicating with the external air by the wind- 
pipe and its ramifications. 

Respiration is performed by the agency of the muscles which lie between 
and about the ribs, and by the diaphragm. The lungs are not nearly emptied 
of air at each expiration. Under ordinary circumstances about 15 cubic 
inches only are thrown out, while by a forced effort as much as 50 or GO 
cubic inches may be expelled. This is repeated about 18 times per minute 
when the individual is tranquil and undisturbed. 

The expired air is found to have undergone a remarkable change; it is 
loaded with aqueous vapour, while a very large proportion of oxygen has 
disappeared, and its place been supplied by carbonic acid ; air once breathed 
containing enough of that gas to extinguish a taper. The total volume of 
the air seems to undergo but little change in this process, the carbonic acid 
being about equal to the oxygen lost. This, however, is found to depend 
very much upon the nature of the food ; it is likely that when fatty sub- 
stances, containing much hydrogen, are used in large quantities, a disappear- 
ance of oxygen will be observed. Nitrogen is in small quantity exhaled from 
the blood. In health no nitrogen is absorbed ; the food invariably containing 
more of that element than the excretions. 

Whatever may be the difficulties attending the investigation of these sub- 
jects, — and difficulties there are, as the discrepant results of the experiments 
prove, — one thing is clear: namely, that quantities of hydrogen and carbon 
are daily oxidized in the body by the free oxygen of the atmosphere, and 
their products expelled from the system in the shape of water and carbonic 
acid. Now, if it be true that the heat developed in the act of combination is 
a constant quantity, and no proposition appears more reasonable, the high 
temperature of the body may be the simple result of this exertion of chemi- 
cal force. 

The oxidation of combustible matter in the blood is effected in the capil- 
laries of the whole body, not in the lungs, the temperature of which does* 
not exceed that of the other parts. The oxygen of the air is taken up in the 
lungs, and carried by the blood to the distant capillary vessels ; by the aid 
of which, secretion, and all the mysterious functions of animal life, are un- 
doubtedly performed: here the combustion takes place, although how this 
happens, and what the exact nature of the combustible may be, beyond the 
simple fact of its containing carbon and hydrogen, yet remains a matter of 
conjecture. The carbonic acid produced is held in solution by the now 
venous blood, and probably confers, in great measure, upon the latter its 
dark colour and deleterious action upon the nervous system. Once more 
poured into the heart, and by that organ driven into the second set of capil- 
laries bathed with atmospheric air, this carbonic acid is conveyed outwards. 



FUNCTION OF RESPIRATION. 507 

tlircmgh the wet membrane, by a kind of false diffusion, constantly observed 
under such circumstances ; "while at the same time oxygen is, by similar 
means, carried inwards, and the blood resumes its bright red colour, and its 
capability of supporting life. Much of this oxygen is, no doubt, simply dis- 
solved in the serum ; the corpuscles, according to Professor Liebig, act as 
carriers of another portion, in virtue of the iron they contain, that metal 
being alternately in the state of sesquioxide, and of carbonate of the pro- 
toxide, — of sesquioxide in the arteries, and of carbonate of protoxide in the 
veins, by loss of oxygen, and acquisition of carbonic acid. M. Mulder con- 
siders the fibrine to act in the same manner ; being true fibrin in the veins, 
and, in part at least, an oxide of proteine in the arteries. 

It would be very desirable to show, if possible, that the quantity of com- 
bustible matter daily burned in the body is adequate to the production of 
the heating effects observed. Something has been done with respect to the 
carbon. Comparison of the quantities and composition of the food con- 
sumed by an individual in a given time, and of the excretions, shows an 
excess of carbon in the former over the latter, amounting, in some cases, 
according to Liebig's high estimate, 1 to 14 ounces ; the whole of which is 
thrown ofi° in the state of carbonic acid, from the lungs and skin, in the 
space of twenty-four hours. This statement applies to the case of healthy, 
vigorous men, much employed in the open air, and supplied with abundance 
of nutritious food. Females, and persons of weaker habit, who follow in- 
door pursuits in warm rooms, consume a much smaller quantity ; their 
respiration is less energetic and the heat generated less in amount. Those 
who inhabit very cold countries are well known to consume enormous quan- 
tities of food of a fatty nature, the carbon and hydrogen of which are, 
without doubt, chiefly employed in the production of animal heat. These 
people live by hunting ; the muscular exertion required quickens and 
deepens the bre/ithing ; while, from the increased density of the air, a 
greater weight of oxygen is taken into the lungs, and absorbed into the 
blood at each inspiration. In this manner the temperature of the body is 
kept up, notwithstanding the piercing external cold ; a most marvellous 
adjustment of the nature of the food, and even of the inclinations and 
appetite of the man, to the circumstances of his existence, enable him to 
bear with impunity an atmospheric temperature which would otherwise 
injure him. 

The carbon consumed in respiration in one day by a horse moderately 
fed, amounted, in a valuable experiment of M. Boussingault, to 77 ounces ; 
that consumed by a cow, to 70 ounces. The determination was made in the 
manner just mentioned, viz., by comparing the quantity and composition of 
the food. 

Chyle. — A specimen, examined by MM. Tiedemann and Gmelin, taken 
from the thoracic duct of a horse, was found closely to resemble, in compo- 
sition and properties, ordinary blood ; the chief difference was the compara- 
tive absence of colouring matter, the chyle having merely a reddish-white 
tint. It coagulated, after standing four hours, and gave a red-coloured clot, 
small in quantity, and a turbid, reddish-yellow serum. The milky appear- 
ance of chyle is due to fat globules, which sometimes confei ;he same 
character upon the serum of blood. 

Lymph. — Under the name of lymph, two or more fluids, very different in 
their nature, have been confounded, namely, the fluid taken up by the absor- 
bents of the alimentary canal, which is simply chyle, containing both fibrin 
and albumin, and the fluid poured out, sometimes in prodigious quantities, 
from serous membranes, which is a very dilute solution of albumin, contain 

1 Animal Chemistry, p. 14. 




508 M i l 

ing a portion of soluble salts of the blood. The liquor amnii of tbe preg 
nnnt female, and the fluid of dropsy, are of this character. 

Mucus and Tus. — The slimy matter effused upon the surface of •various' 
mucous membranes, as the lining of the alimentary canal, that of the blad- 
der, of the nose, lungs, &c, to which the general name mucus is given, 
probably varies a good deal in its nature in different situations. It is com- 
monly either colourless or slightly yellow, and translucent or transparent; it 
is quite insoluble in water, forming, in the moist state, a viscid, gelatinous 
mass. In dilute alkalis it dissolves with ease, and the solution is precipi- 
tated by an addition of acid. . 

Pus, the natural secretion of a wounded or otherwise injured surface, is 
commonly a creamy, white, or yellowish 
liquid, which, under the microscope, ap- 
pears to consist of multitudes of minute 
globules (fig. 175, a) ; dilute acetic acid 
renders them transparent, and shows the 
internal nuclei (b). It is neither acid nor 
alkaline. Mixed with water, it communi- 
cates a milkiness to the latter, but after a 
time subsides. Caustic alkali does not 
dissolve pus, but converts it into a trans- 
parent, gelatinous substance, which can be drawn out into threads. The 
peculiar ropincss thus produced with an alkali is not peculiar to pus. Healthy 
mucus owes its sliminess to an alkaline fluid acting on the mucous globules. 

MILK, BILE, URINE, AND URINARY CALCULI. 

Milk. — The peculiar special secretion destined for the nourishment of the 
young is, so far as is known, very much the same in flesh-eating animals 
and in those which live exclusively on vegetable food. The proportions of 
the constituents may, however, sometimes differ to a considerable extent. 
It will be seen hereafter that the substances present in milk are wonderfully 
adapted to its office of providing materials for the rapid growth and develop- 
ment of the animal frame. It contains an azotized matter, casein, nearly 
identical in composition with muscular flesh, fatty principles, and a peculiar 
sugar, and lastly, various salts, among which may be mentioned phosphate 
of lime, held in complete solution in a slightly alkaline liquid. This last is 
especially important to a process then in activity, the formation of bone. 

The white, and almost opaque, appearance of 

s milk is an optical illusion; examined by a mi- 

© @ o oo croscope of even moderate power, it is seen to 

Q ° o m q2°& °°® consist of a perfectly transparent fluid, in which 

o °s 9 @® ^ fl° at anou t numbers of transparent globules 

tfJU?®® o® " ?©©® ® ( fi &- 17G ) ; tnese consist of fat » surrounded by 

® ?-y3@ni° °r® °%<h an a lhuminous envelope, which can be broken 

J^®©!<3> f ° ®° 0o mechanically, as in churning, or dissolved by 

G ° 00 d|rf ^0° ^®9 e ° the chemical action of caustic potassa, after 

° o®®o ®e§^P y o which, on agitating the milk with ether, the fat 

can be dissolved. 

"When milk is suffered to remain at rest some 
hours, at the ordinary temperature of the air, a large proportion of the fat 
globules collect at the surface into a layer of cream; if this be now removed 
and exposed for some time to strong agitation, the fat-globules coalesce into 
a mass, and the remaining watery liquid is expelled from between them and 
separated. The bullcr so produced must be thoroughly washed with cold 
water, to remove as far as possible the last traces of casein, which readily 
putrefies, and would in that case spoil the whole. A little salt is usually added. 



AND URINARY CALCULI. 509 

Ordinary butter still, however, contains some butter-milk, and when in- 
tended for keeping should be clarified, as it is termed, by fusion. The 
Watery part then subsides, and carries with it the residue of the azotized 
matter. The flavour is unfortunately somewhat impaired by this process. 
The consistence of butter, in other words, the proportions of margarin and 
olein, is dependent upon the season, or more probably upon the kind of 
food ; in summer the oily portion is always more considerable than in win- 
ter. The volatile odoriferous principle of butter, butyrin, has been already 
referred to. 

The casein of milk, in the state of cheese, is in many countries an im- 
portant article of food. The milk is usually heated to about 120° (49°C), 
and coagulated by rennet, or an infusion of the stomach of the calf in water ; 
the curd is carefully separated by a sieve from the whey, mixed with a due 
proportion of salt, and sometimes some colouring-matter, and then subjected 
to strong and increasing pressure. The fresh cheese so prepared being con- 
stantly kept cool and dry, undergoes a particular kind of putrefactive fer- 
mentation, very little understood, by which principles are generated which 
communicate a particular taste and odour. The goodness of cheese, as well 
as much of the difference of flavour perceptible in different samples, de- 
pends in great measure upon the manipulation ; the best kinds contain a 
considerable quantity of fat, and are made with new milk ; the inferior 
descriptions are made with skimmed milk. 

Some of the Tartar tribes prepare a kind of spirit from milk by suffering 
it to ferment, with frequent agitation. The casein converts a part of the 
milk-sugar into lactic acid, and another part into grape-sugar, which in 
turn becomes converted into alcohol. Mare's milk is said to answer better 
for this purpose than that of the cow. 

In a fresh state, and taken from a healthy animal, milk is always feebly 
alkaline. When left to itself, it very soon becomes acid, and is then found 
to contain lactic acid, which cannot be discovered in the fresh condition. 
The alkalinity is due to the soda which holds the casein in solution. In 
this soluble form casein possesses the power of taking up and retaining a 
very considerable quantity of phosphate of lime. The density of milk 
varies exceedingly; its quality usually bears an inverse ratio to its quantity. 
From an analysis of cow-milk in the fresh state by M. Haidlen, 1 the follow- 
ing statement of its composition in 1000 parts has been deduced: — 

Water 873-00 

Butter 30 00 

Casein 48-20 

Milk-sugar 43-90 

Phosphate of lime 2-31 

" magnesia , 42 

" iron 0-07 

Chloride of potassium 1-44 

Sodium 0-24 

Soda in combination with casein 0-42 

1000-00 

Human milk is remarkable for the difficulty with which it coagulates ; it 
generally contains a larger proportion of sugar than cow-milk, but scarcely 
differs in other respects. 

Bile. — This is a secretion of a very different character from the pre- 
ceding ; the largest internal organ of the body, the liver, is devoted to its 

1 Annaien der Chemie und Pharmacie, xlv. 263. 

43* 



510 MIL 

preparation, which is said to take place from venous, instead of arterial 
blood. The composition of the bile has been made the subject of much in- 
vestigation ; the following is a summary of the most important facts which 
have been brought to light. 

In its ordinary state, bile is a very deep yellow, or greenish, viscid, trans- 
parent liquid, which darkens by exposure to the air, and undergoes changes 
which have been yet imperfectly studied. It has a disagreeable odour, a 
most nauseous, bitter taste, a distinctly alkaline reaction, and is miscible 
with water in all proportions. When evaporated to dryness at 212° (100°C), 
and treated with alcohol, the greater part dissolves, leaving behind an in- 
soluble jelly of mucus of the gall-bladder. This alcoholic solution contains 
colouring-matter and cholesterin; from the former it maybe freed by diges- 
tion with animal charcoal, and from the latter by a large admixture of ether, 
in which the bile is insoluble, and separates as a thick, syrupy, and nearly 
colourless liquid. The colouring-matter may also be precipitated by baryta- 
water. 

Pure bile thus obtained, when evaporated to dryness by a gentle heat, 
forms a slightly yellowish brittle mass, resembling gum-Arabic. It is com- 
pletely soluble in water and absolute alcohol. The solution is not affected 
by the vegetable acids ; hydrochloric and sulphuric acids, on the contrary, 
give rise to turbidity, either immediately or after a short interval. Acetate 
of lead partially precipitates it ; the tribasic acetate precipitates it com- 
pletely ; the precipitate is readily soluble in acetic acid, in alcohol, and to a 
certain extent in excess of acetate of lead. "When carbonized by heat, and 
incinerated, bile leaves between 11 and 12 per cent, of ash, consisting chiefly 
of carbonate of soda, with a little common salt and alkaline phosphate. 
The recent beautiful researches of Strecker, show that bile is essentially a 
mixture of the soda-salts of two peculiar conjugate acids very distinctly 
resembling the resinous and fatty acids. One of these contains nitrogen, 
but no sulphur, and is termed cholic acid, or better, glycho-cholalic, being a 
conjugated compound of a non-nitrogenous acid, cholalic acid, 1 with the nitro- 
genetted substance glycocine (see page 501), the other containing nitrogen 
and sulphur, has received the name choleic acid, or better, tauro-cholalic acid, 
being a conjugated compound of the same cholalic acid with a body to be 
presently described under the name of taurin, containing both nitrogen and 
sulphur. The relative proportion in which these acids occur in bile, remains 
pretty constant with the same animal, but varies considerably with different 
classes of animals. 

Glyco-cholalic acid may be thus obtained : — When ox bile is perfectly 
dried and extracted with cold absolute alcohol, and after filtration is mixed 
with ether, it first deposits a brownish tough resinous mass, and after some 
time, stellated crystals which consist of glyco-cholalate of soda and potassa. 
These mixed crystals were first obtained by Platner, and they compose his 
Bo-called crystallized bile. 

Glyco-cholalic acid may be obtained by decomposing the glyco-cholalate 
of soda by sulphuric acid ; it crystallizes in fine white needles of a bitterish 
sweet taste, is soluble in water and alcohol, but onty slightly in ether, and 
has a strong acid reaction. It is represented by the formula C 52 IT 42 NO u ,HO. 
When boiled with a solution of potassa, the acid divides into cholalic acid 
C 4ft H 39 9 ,HO, and glycocine or gelatin-sugar: — 

C 52 H 42 NO n ,HO-f2HO = C 48 H SB 9 ,HO + C 4 n 5 N0 4 



Glyco-cholalic acid. Cholalic acid. Glycocine. 



Also callrd cholic acid by some authors. 



AND URINARY CALCULI. 511 

Boiled with concentrated sulphuric or hydrochloric acids, it yields likewise 
glycocine, but instead of cholalic acid, another -white amorphous acid, cho- 
loidinic acid (C 48 H 39 9 = cholalic acid — 1 eq. of water), or if the ebullition 
has continued for some time, a resinous substance, from its insolubility in 
water called dyslysin, (C 4S H 36 6 '= cholalic acid — 4 eq. of water.) 

Tauro-cholalic acid is thus procured. Ox bile is freed as far as pos- 
sible from glyco-cholalic acid by means of neutral acetate of lead, and it is 
then precipitated by basic acetate of lead, to which a little ammonia is 
added. The precipitate is decomposed by carbonate of soda, when tolerably 
pure tauro-cholalate of soda is obtained. By decomposing the tauro-cholalate 
of lead by sulphuretted hydrogen, tauro-cholalic acid is liberated. This 
substance, however, which was previously called choleic acid and bilin, has 
never been obtained in the pure state. Its formula, as inferred from the 
study of its products of decomposition, would be C 52 H 44 NS 2 T3 ,HO. When 
boiled with alkalis it divides into cholalic acid and taurine : — 

C 52 H 44 NS 2 13 ,HO-f2IIO = C 48 H 39 9 ,HO-f C 4 H 7 NS 2 6 

Tauro-cholalic acid. Cholalic acid. Taurin. 

With boiling acids it gives likewise taurin, but instead of cholalic acid, 
either choloidinic acid or dy sly sin, according to the duration of the ebulli- 
tion. 

Taurin, C 4 H 7 NS 2 6 , crystallizes in colourless regular hexagonal prisms, 
which have no odour and very little taste. It is neutral to test-paper, and 
permanent in the air. W T hen burnt, it gives rise to much sulphurous acid. 
It contains upwards of 25 per cent, of sulphur. It is easily prepared by 
boiling purified bile for some hours with hydrochloric acid. After filtration 
and evaporation, the acid residue is treated with five or six times its bulk 
of boiling alcohol, from which the taurin separates on cooling. 

Cholalic or cholic acid, C 4S H 39 9 ,HO, crystallizes in tetrahedra. It 
is soluble in sulphuric acid, and on the addition of a drop of this acid and 
a solution of sugar (1 part of sugar to 4 parts of water), a purple-violet 
colour is produced, -which constitutes Pettenkofers test for bile. At 383° 
(195°C) it loses an atom of water, and is converted into chloloidinic acid, 
which change, as has been pointed out, is also produced by ebullition with 
acids. 

Cholalic acid is best obtained by boiling the resinous mass precipitated by 
ether from the alcoholic solution of the bile with a dilute solution of potassa 
for 24 or 36 hours, till the amorphous potassa-salt that has separated begins 
to crystallize. The dark-coloured soft mass removed from the alkaline 
liquid, dissolved in water, and hydrochloric acid added, a little ether causes 
the deposition of the cholalic acid in crystals. 

One of the colouring-matters of the bile forms the chief part of the con- 
cretions sometimes met with in the gall-bladders of oxen, and which are much 
valued by painters in water-colours, as forming a magnificent yellow pigment. 
It dissolves in caustic alkali without change of colour, and when mixed with 
excess of nitric acid becomes successively green, blue, violet, red, and even- 
tually yellow. The composition of this substance is unknown. Another 
colouring-matter is dark green, and is considered by Berzelius, as identical 
with the pigment of leaves. 

According to the researches of Strecker and Gundelach, pigs' bile differs 
from the bile of other animals. This bile contains an acid, to which the 
name hyocholic acid has been given, which may be prepared in the following 
manner: — fresh pigs' bile is mixed with a solution of sulphate of soda, the 
precipitate obtained is dissolved in absolute alcohol, and decolorized by 
animal charcoal. From this solution ether throws down a soda-salt, yield- 



612 MILK, BILE, AND URINE. 

ing, on addition of sulphuric acid, hyocholic acid as a resinous mass, which 
is dissolved in alcohol and re-precipitated by water. 

Hyocholic acid contains C 54 H 43 NO 10 . When heated with solutions of the 
alkalis, the acid undergoes a decomposition perfectly analogous to that of 
glyco-cholalic acid, hyocholic acid, splitting into glycocine and a crystalline 
acid, very soluble in alcohol, less so in ether, which has been termed hyocho- 
lalic acid. This substance contains C 50 H 39 O 7 ,HO, and the change is repre- 
sented by the following equation: — 

C5 4 H 43 NO 10 -f-2HO = e 50 F 39 O 7 ,HO + C 4 H 5 N0 4 

Hyocholic acid. Hyocholalic acid. Glycocine. 

Hence hyocholic acid might be called glyco-hyocholalic acid. When boiled 
with acids, glyco-hyocholalic acid yields likewise glycocine, but instead of 
hyocholalic acid, a substance representing the dyslvsin of the ordinary bile, 
which might be termed hyodyslysin. The composition of hyodyslyin is 
C 50 Hj g O 6 = hyocholalic acid — 2 eq. HO. 

Pigs' bile contains a very trifling quantity of sulphur, probably in the form 
of a sulphuretted acid corresponding to the tauro-cholalic acid of ox-bile. 
Strecker believes this acid to contain C 54 H 45 NS 2 12 : it might be called tauro- 
liyocholalic acid, which when boiled with an alkali would yield taurin and 
hyocholalic acid. The sulphuretted acid must be present in pigs' bile in 
very minute quantity ; it is even less known than tauro-cholalic acid. 

The once celebrated oriental bezoar-stones are biliary calculi, said to be 
procured from a species of antelope ; they have a brown tint, a concentric 
structure, and a waxy appearance, and consist essentially of a peculiar and 
definite crystallizable principle called lithofellinic acid. To procure this sub- 
stance, the calculi are reduced to powder and exhausted with boiling al- 
cohol ; the dark solution is decolorized by animal charcoal, and left to eva- 
porate by gentle heat, whereupon the lithofellinic acid is deposited in small, 
colourless, transparent six-sided prisms. It is insoluble in water, and with 
difficulty soluble in ether, but dissolves with ease in alcohol : it melts at 
202° (95° -5C), and at a higher temperature burns with a smoky flame, 
leaving but little charcoal. Lithofellinic acid dissolves without decompo- 
sition in concentrated acetic acid, and in oil of vitriol ; it forms a soluble 
salt with potassa, and dissolves also in ammonia, but crystallizes out un- 
changed on evaporation. By analysis, lithofellinic acid is found to consist 
of C 40 H 35 O 7 ,HO. 

Urine. — The urine is the great channel by which the azotized matter of 
those portions of the body which have been taken up by the absorbents is 
conveyed away and rejected from the system in the form of urea. It serves 
also to remove superfluous water, and foreign soluble matters which get in- 
troduced into the blood. 

The two most remarkable and characteristic constituents of urine, urea 
and uric acid, have already been fully described ; in addition to these, it 
contains sulphates, chlorides, phosphates of lime, and magnesia, alkaline 
salts, and certain yet imperfectly known principles, including an odoriferous 
and a colouring substance (see foot-note to p. 513). 

Healthy human urine is a transparent, light amber-coloured liquid, which, 
while warm, emits a peculiar, aromatic, and not disagreeable odour. This 
is lost on cooling, while the urine at the same time occasionally becomes 
turbid from a deposition of urate of ammonia, which re-dissolves with slight 
elevation of temperature. It is very decidedly acid to test-paper; 1 this 
acidity has been ascribed to acid phosphate of soda, to free uric acid, and 

* The degree of acidity appears to be constantly changing. See Philosophical Trans. 1849, 



MILK, BILE, AND URINE. 513 

to free lactic acid ; lactic acid can, however, hardly co-exist with urate of 
ammonia, and the amorphous buff-coloured deposit obtained from fresh urine 
by spontaneous evaporation in vacuo is not uric acid, but the ammonia-salt 
of that substance, modified as to crystalline form by the presence of minute 
quantities of chloride of sodium. That a free acid is sometimes present in 
the urine, is certain ; in this case, the reaction to test-paper is far stronger, 
and the liquid deposits on standing little, red, hard crystals of uric acid ; 
but this is no longer a normal secretion. 

An alkaline condition of the urine from fixed alkali is sometimes met with. 
Such alkalinity can always be induced by the administration of neutral 
potassa or soda-salts of a vegetable acid, as tartaric or acetic acid ; the acid 
of the salt is burned in the blood in the process of respiration, and a por- 
tion of the base appears in the urine in the state of carbonate. The urine 
is often alkaline in cases of retention, from carbonate of ammonia produced 
by putrefaction in the bladder itself; but this is easily distinguished from 
alkalinity from fixed alkali, in which it is secreted in that condition. 

The density of the urine varies from 1-005 to 1-030; about 1-020 to 1-023 
may be taken as the average specific gravity. A high degree of density in 
urine may arise from an unusually large proportion of urea; in such a case, 
the addition of nitric acid will occasion an almost immediate production of 
crystals of nitrate of urea, whereas with urine of the usual degree of con- 
centration many hours will elapse before the nitrate begins to separate. The 
quantity passed depends much upon circumstances, as upon the activity of 
the skin; it is usually more deficient in quantity and of higher density in 
summer than in winter. Perhaps about 32 ounces in the 24 hours may be 
assumed as a mean. 

When kept at a moderate temperature, urine, after some days, begins to 
decompose ; it exhales an offensive odour, becomes alkaline from the pro- 
duction of carbonate of ammonia, and turbid from the deposition of 
earthy phosphates. The carbonate of ammonia is due to the putrefactive 
decomposition of the urea, which gradually disappears, the ferment, or active 
agent of the change, being apparently the mucus of the bladder, a portion 
of which is always voided with the urine. It has been found also that the 
yellow adhesive deposit from stale urine is a most powerful ferment to the 
fresh secretion. In this putrefied state urine is used in several of the arts, 
as in dyeing ; and forms, perhaps, the most valuable manure for land known 
to exist. 

Putrid urine always contains a considerable quantity of sulphide of am- 
monium ; this is formed by the de-oxidation of sulphates by the organic 
matter. The highly offensive odour and extreme pungency of the decom- 
posing liquid may be prevented by previously mixing the urine, as Liebig 
suggests, with sulphuric or hydrochloric acid, in sufficient quantity to satu- 
rate all the ammonia that can be formed. 

The following is an analysis of human urine, by Berzelius. 1000 part?, 
contained 

Water.. 93300 

Urea 3010 

Lactates and extractive matter 1 17-14 

1 All dark-coloured, uncrystallizable substances, soluble both in water and alcohol, were 
confounded by the old chemists under the general name of extractive matter. The progress 
of modern science constantly tends to extricate from this confused mass one by one the 
many definite organic principles therein contained in a more or less modified form, and to 
restrict within narrower limits the application of the term. In the above instance, the 
colouring matter of the urine, and it may be several other substances, are involved. 

Professor Liebig states that all his endeavours to obtain direct evidence of the existence 
of lactic acid in the urine, either in a fresh or putrid state, completely failed. Putrid urine 



514 MILK, BILE, AND URINE. 

Uric acid , 100 

Sulphates of potassa and soda 6-87 

Phosphate of soda 2-92 

" ammonia 1-65 

" lime and magnesia 1-00 

Chloride of sodium 4-45 

Sal-ammoniac 1-50 

Silica 003 

Mucus of bladder 0-32 



1000-00 



In certain states of disorder and disease substances appear in the urine 
which are never present in the normal secretion ; of these the most common 
is albumin. This is easily detected by the addition of nitric acid in excess, 
which then causes a white cloud or turbidity, which is permanent when 
boiled, or by corrosive sublimate, the urine being previously acidified by a 
little acetic acid ; boiling causes usually a precipitate which is not dissolved 
by a drop or two of acid. Mere turbidity by boiling is no proof of albumin, 
ibz earthy phosphates being often thrown down from nearly neutral urine 
u^der such circumstances ; the phosphatic precipitate is, however, instantly 
di 'solved by a drop of nitric acid. 

In diabetes the urine contains grape-sugar, the quantity of which com- 
monly increases with the progress of the disease, 
Tig. 177. until it becomes enormous, the urine acquiring a 

density of 1040 and beyond. It does not appear 
that the urea is deficient absolutely, although 
more difficult to discover from being mixed with 
such a mass of syrup. The smallest trace of 
sugar may be discovered in urine by Trommer's 
test, (fig. 177,) formerly mentioned : a few drops 
of solution of sulphate of copper are added to 
the urine, and afterwards an excess of caustic 
potassa ; if sugar be present, a deep-blue liquid 
results, which, on boiling, deposits red suboxide 
of copper. With proper management, this test 
is very valuable ; it will even detect sugar in the 
blood of diabetic patients.* Urine containing 
sugar, when mixed with a little yeast, and put 
in a warm place, readily undergoes vinous fer- 
mentation, and afterwards yields, on distillation, 
weak alcohol, contaminated with ammonia. 
The urine of children is said sometimes to contain benzoic acid; it is pos- 
sible that this may be hippuric acid. When benzoic acid is taken, the urine 
after a few hours yields on concentration, and the addition of hydrochloric 
acid, needles of hippuric acid, soiled by adhering uric acid. 

yielded a volatile acid in a notable quantity, -which turned out to be acetic acid; a little ben- 
zoic acid was also noticed, and traced to a small amount of hippuric acid in the recent urine. 
The acid reaction of urine is ascribed to an acid phosphate of soda, produced by the partial 
decomposition of some of the common phosphate, the reaction of which is alkaline, by the 
organic acids (\iric and hippuric) generated in the system, aided by the sulphuric acid con- 
stantly produced by the oxidation of the protein-compounds of the food, or rather of the 
body. — Lancet, June. 1844. 
_ Still more recently Liebig has announced the discovery in the urine of kreatin and krea- 
tinine, already described. Putrid urine contains kreatinine only. 

1 Dr. Benee Jones, Med. Chirur. Trans, vol. xxvi. Great care must be taken in using this 
*est. -which depends on the Instantaneous reduction of the oxide of copper. By long boiling 
fery many organic substances produce this reaction. 




URINARY C ALCU LI, 



515 



The deposit of buff-coloured or pinkish amorphous urate of ammonia, 
which so frequently occurs in urine upon cooling, after unusual exercise or 
slight derangements of health, may be at once distinguished from a deposit 
of ammonio-magnesian phosphate by its instant disappearance on the appli- 
cation of heat. The earthy phosphates, besides, are hardly ever deposited 
from urine which has an acid reaction. The nature of the red colouring 
matter which so often stains urinary deposits, especially in the case of free 
uric acid, is yet unknown. 

The yellow principle of bile has been observed in urine in severe cases of 
jaundice. 

The urine of the carnivorous mammifera is small in quantity, and highly 
acid ; it has a very offensive odour, and quickly putrefies. In composition 
it resembles that of man, and is rich in urea. In birds and serpents the 
urine is a white pasty substance, consisting almost entirely of urate of ammo- 
nia. In herbivorous animals it is alkaline and often turbid from earthy car- 
bonates and phosphates ; urea is still the characteristic ingredient, while of 
uric acid there is scarcely a trace ; hippuric acid is usually, if not always, 
present, sometimes to a very large extent. When the urine putrefies, this 
hippuric acid, as already noticed, becomes changed to benzoic acid. 

Urinary calculi. — Stony concretions, differing much in physical charac- 
ters and in chemical composition, are unhappily but too frequently formed 
in the bladder itself, and give rise to one of the most distressing complaints 
to which humanity is subject. Although many endeavours have been made 
to find some solvent or solvents for these calculi, and thus supersede the 
necessity of a formidable surgical operation for their removal, success has 
been but very partial and limited. 

Urinary calculi are generally composed of concentric layers of crystalline 
or amorphous matter, of various degrees of hardness. Very frequently the 
central point or nucleus is a small foreign body; curious illustrations of this 
will be seen in any large collection. Calculi are not confined to man; the 
lower animals are subject to the same affliction ; they have been found in 
horses, oxen, sheep, pigs, and almost constantly in rats. 

The following is a sketch of the principal characters of the different varie- 
ties of calculi: — 

1. Uric Acid. — These are among the most common 
smooth or warty, of yellowish or brownish tint ; 
they have an imperfectly crystalline, dis- 
tinctly concentric structure, and are tolerably 
hard. Fig. 178. Before the blowpipe the uric 
acid calculus burns away, leaving no ash. It 
is insoluble in water, but dissolves with facility 
in caustic potassa, with but little ammoniacal 
odour; the solution mixed with acid gives a 
copious white curdy precipitate of uric acid, 
which speedily becomes dense and crystalline. 
Cautiously heated with nitric acid, and then 
mixed with a little ammonia, it gives the cha- 
racteristic reaction of urie acid, viz., deep pur- 
ple-red murexide. 

2. Urate of Ammonia. — Calculi of urate of 
ammonia much resemble the preceding ; they 
are easily distinguished, however. Fig. 179. 
The powder boiled in water dissolves, and the 
solution gives a precipitate of uric acid when 
mixed with hydrochloric acid. It dissolves 
also in hot carbonate of potassa with copious 
^volution of ammonia. 



externally they are 



Fi£. 178. 




Fig. 179. 




&m 



616 



URINARY CALCULI. 




m^ 



Fig. 181. 



3. Fusible Calculus ; Phosphate of Lime with Phosphate of Magnesia and 
Ammonia. — This is one of the most common kinds. 

Fig- ISO. The stones are usually white or pale-coloured, 

smooth, earthy, and soft ; they often attain a 
large size. Fig. 180. Before the blowpipe this 
substance blackens from animal matter which 
earthy calculi always contain ; then becomes 
white, and melts to a bead with comparative 
facility. It is insoluble in caustic alkali, but 
readily soluble in dilute acids, and the solution 
is precipitated by ammonia. Calculi of unmixed phosphate of lime are rare, 
as also those of phosphate of magnesia and ammonia ; the latter salt is 
sometimes seen forming small, brilliant crystals in cavities in the fusible 
calculus. 

4. Oxalate of Lime Calculus: Mulberry Calculus. — The latter name is de- 
rived from the rough, warty character, and dark 
blood-stained aspect of this variety; it is perhaps 
the worst form of calculus. Fig. 181. It is ex- 
ceedingly hard ; the layers are thick and imper- 
fectly crystalline. Before the blowpipe the oxa- 
late of lime burns to carbonate by a moderate 
red-heat, and, when the flame is strongly urged, 
to quicklime. It is soluble in moderately strong 
hydrochloric acid by heat, and very easily in ni- 
tric acid. When finely powdered and long boiled 
in a solution of carbonate of potassa, oxalate of 

potassa may be discovered in the filtered liquid, 
when carefully neutralized by nitric acid, by white precipitates with solu- 
tions of lime, lead, and silver. A sediment of oxalate of lime in very minute, 
transparent, octahedral crystals, only to be seen by the microscope, is of 
common occurrence in urine in which a tendency to urate of ammonia 
deposits exists. 

5. Cystic and Xanthic Oxides have already been described; they are very 
rare, especially the latter. Calculi of cystic oxide are very crystalline, and 
often present a waxy appearance externally ; sediments of cystic oxide are 
sometimes met with. As before mentioned, this substance is a definite crys- 
tallizable organic principle, containing sulphur to a large amount ; it is solu- 
ble both in acids and alkalis. "When the solution in nitric acid is evaporated 
to dryness, it blackens ; when dissolved in a large quantity of caustic potassa, 
a drop of solution of acetate of lead added, and the whole boiled, a black pre- 
cipitate containing sulphide of lead makes its appearance. By these charac- 
ters cystic oxide is easily recognized. 

Xanthic oxide, also a definite organic principle, is distinguished by the 
peculiar deep-yellow colour produced when its solution in nitric acid is evapo- 
rated to dryness ; it is soluble in alkalis, but not in hydrochloric acid. 

Very many calculi are of a composite nature, the composition of the dif- 
ferent layers being occasionally changed, or alternating ; thus, urate of am- 
monia and oxalate of lime are not unfrequently associated in the same 
stont,. 




NERVOUS SUBSTANCE ; MEMBRANOUS TISSUE ; BONES. 

Nervous substance. — The brain and nerves consist of an albuminous 
substance, containing several remarkable fatty principles, capable of being 
extracted by alcohol and ether, some of which are yet very imperfectly 
known, and about 80 per cent, of water. Besides cholesterin, and a little 
ordinary fat, separated in the manner mentioned, M. Fremy describes two 



MEMBRANOUS TISSUES. 517 

new bodies,' cerebric acid and oleo-phosphoric acid. The first is solid, white, 
and crystalline, soluble without difficulty in boiling alcohol, and forming 
with hot water a soft, gelatinous mass. It melts when heated, and decom- 
poses almost immediately afterwards, exhaling a peculiar odour, and leaving 
a quantity of charcoal which contains free phosphoric acid, and is in conse- 
quence very difficult to burn. It combines with the alkalis, but forms in- 
soluble compounds. Cerebric acid contains in 100 parts — 

Carbon 66-7 

Hydrogen 10-6 

Nitrogen , 2-3 

Oxygen 19-5 

Phosphorus 0-9 

-100-0 
The oleo-phosphoric acid has been even less perfectly studied than the 
preceding substance. It is of soft oily consistence, soluble in hot alcohol 
and ether, and saponifiable. When boiled with water, it is resolved into a 
fluid neutral oil, called cerebrolein, and phosphoric acid, which dissolves. 

The oily matter of the brain is sufficient in quantity to form with the 
albuminous portion a kind of emulsion, which, when beaten up, remains 
long suspended in water. 

Membranous tissues ; skin. — The composition of the many gelatin- 
giving tissues of the body is in great measure unknown ; even that of gela- 
tin itself is very doubtful,, as several different substances may very possibly 
be confounded under this name. Dr. Scherer 2 has given, among many 
others, analyses of the middle coat of the arteries, which will serve as an 
example of a finely organized, highly elastic membrane, and of the coarse 
epidermis of the sole of the foot, with which it may be contrasted : — 

Artery coat. Epidermis. 

Carbon 53-75 51-04 

Hydrogen 7-08 6-80 

Nitrogen 15-36 17-23 

Oxygen 2381 24-93 

100-00 100-00 

A little sulphur was found in the epidermis. Hair, horn, nails, wool, and 
feathers have a nearly similar composition ; they all dissolve with disen- 
gagement of ammonia in caustic potassa, and the solution, when mixed with 
acid, deposits a kind of protein common to the whole. It is useless assign- 
ing formulas to substances yet so little understood. 

The principle of tanning, of such great practical value, is easily explained. 
"When the skin of an animal, carefully deprived of hair, fat, and other im- 
purities, is immersed in a dilute solution of tannic acid, the animal matter 
gradually combines with that substance as it penetrates inwards, forming a 
perfectly insoluble compound, which resists putrefaction completely; this is 
leather. In practice, lime-water is used for cleansing and preparing the 
skin, and an infusion of oak-bark, or sometimes catechu, or other astringent 
matter, for the source of tannic acid. The process itself is necessarily a 
slow one, as dilute solutions only can be safely used. Of late years, how- 
ever, various contrivances, some of which show great ingenuity, have been 
adopted with more or less success, for quickening the operation. All leather 
is not tanned ; glove-leather is dressed with alum and common salt, and 

1 Ann. Cbim et Phys. 3rd series, ii. 463. 

2 AnnaJen der Chemie und i'harmacie ; xl. 50. 

44 



518 ANIMAL NUTRITION. 

afterwards treated with a preparation of the yolks. of eggs, which contain 
an albuminous matter and a yellow oil. Leather of this kind still yields a 
size by the action of boiling water. 

Bones. — Bones are constructed of a dense cellular tissue of membra- 
notis matter, made stiff and rigid by insoluble earthy salts, of which phos- 
phate of lime (3CaO,P0 5 ) is the most abundant. The proportions of earthy 
and animal matter vary very much with the kind of bone and with the age 
of the individual, as will be seen in the following table, in which the corres- 
ponding bones of an adult and of a still-born child are compared : — 



Inorganic Organic Inorganic Organic 

matter. matter. matter. matter. 

Femur 62-49 ... 37-51 57-51 ... 42-49 

Humerus 63-02 ... 36-98 58-08 ... 41-92 

Radius 60-51 ... 39-49 56-50 ... 43-50 

Os temporum 63-50 ... 36-50 55-90 ... 44-10 

Costa 57-49 ... 42-51 53-75 ... 46-25 

The bones of the adult being constantly richer in earthy salts than those of 
the infant. 

The following complete comparative analysis of human and ox-bones is 
due to Berzelius : — 

Human bones. Ox-bones. 
Animal matter soluble by boiling .... 32-17 1 oq.qn 

Vascular substance 1*13/ 

Phosphate of lime, with a little ) <q.(U ^7-3^ 

fluoride of calcium / 

Carbonate of lime..... 11-30 , 3-85 

Phosphate of magnesia 1-16 2-05 

Soda, and a little common salt 1-20 3-45 



10000 10000 

The teeth have a very similar composition, but contain less animal matter ; 
their texture is much more solid and compact. The enamel does not contain 
more than 2 or 3 per cent, of animal matter. 

ON THE FUNCTION OF NUTRITION IN THE ANIMAL AND VEGETABLE KINGDOMS. 

The constant and unceasing waste of the animal body in the process of 
respiration, and in the various secondary changes therewith connected, ne- 
cessitates an equally constant repair and renewal of the whole frame by the 
deposition or organization of matter from the blood, which is thus gradually 
impoverished. To supply this deficiency of solid material in the circulating 
fluid is the office of the food. The striking contrast which at first appears 
in the nature of the food of the two great classes of animals, the vegetable 
feeders and the carnivorous races, diminishes greatly on close examination: 
it will be seen, that, so far as the materials of blood, or, in other words, 
those devoted to the repair and sustenance of the body itself, are concerned, 
the process is the same. In a flesh-eating animal great simplicity is observed 
in the construction of the digestive organs : the stomach is a mere enlarge- 
ment of the short and simple alimentary canal ; and the reason is plain : the 
food of the creature, flesh, is absolutely identical in composition with its 
own blood, and with the body that blood is destined to nourish. In the sto- 
mach it undergoes mere solution, being brought into a state fitted for absorp- 
tion by the lacteal vessels, by which it is nearly all taken up, and at once 
conveyed into the blood; the excrements of such animals are little more 



ANIMAL NUTRITION. 519 

than the comminuted bones, feathers, hair, and other matters which refuse 
to dissolve in the stomach. The same condition, that the food employed for 
the nourishment of the body must have the same or nearly the same chemi- 
cal composition as the body itself, is really fulfilled in the case of animals 
that live exclusively on vegetable substances. It has been shown 1 that cer- 
tain of the azotized principles of plants, which often abound, and are never 
altogether absent, have a chemical composition and assemblage of properties 
which assimilate them in the closest manner, and it is believed even identify 
them, with the azotized principles of the animal body ; vegetable albumin, 
fibrin, and casein are scarcely to be distinguished from the bodies of the same 
name extracted from blood and milk. 

If a portion of wheaten flour be made into a paste with water, and cau- 
tiously washed on a fine metallic sieve, or in a cloth, a greyish, adhesive, 
elastic, insoluble substance will be left, called gluten or glutin, and a milky 
liquid will pass through, which by a few hours' rest becomes clear by de- 
positing a quantity of starch. If now this liquid be boiled, it becomes again 
turbid from the production of a flocculent precipitate, which, when collected, 
washed, dried, and purified from fat by boiling with ether, is found to have 
the same composition as animal albumin. The glutin itself is a mixture of 
true vegetable fibrin, and a small quantity of a peculiar azotized matter 
called gliadin, to which its adhesive properties are due. The gliadin may 
be extracted by boiling alcoliol, together with a thick, fluid oil, which is 
separable by ether : it is gluey and adhesive, quite insoluble in water, and, 
when dry, hard and translucent like horn ; it dissolves readily in dilute caus- 
tic alkali, and also in acetic acid. The fibrin of other grain is unaccompa- 
nied by gliadin ; barley and oatmeal yield no glutin, but incoherent filaments 
of nearly pure fibrin. 

Vegetable albumin in a soluble state abounds in the juice of many soft 
succulent plants used for food ; it may be extracted from potatoes by mace- 
rating the sliced tubers in cold water containing a little sulphuric acid. It 
congulates when heated to a temperature dependent upon the degree of con- 
centration, and cannot be distinguished when in this state from boiled white 
of egg in a divided condition. 

Almonds, peas, beans, and many of the oily seeds, contain a principle 
which bears the most striking resemblance to the casein of milk. When a 
solution of this substance is heated, no coagulation occurs, but a skin forms 
on the surface, just as with boiled milk. It is .coagulable by alcohol, and by 
acetic acid : the last being a character of importance. Such a solution mixed 
with a little sugar, an emulsion of sweet almonds, for instance, left to itself, 
soon becomes sour and curdy, and exhales an offensive smell ; it is then found 
to contain lactic acid. 

All these substances dissolve in caustic potassa with production of a small 
quantity of alkaline sulphide ; the filtered solutions mixed with excess of 
acid give precipitates of protein. 

The following is the composition in 100 parts of vegetable albumin and 
fibrin ; it will be seen that they agree very closely with the results before 
given : — 

Albumin. Fibrin. 

Carbon 5501 54-60 

Hydrogen 7-23 7-30 

Nitrogen 15-92 15-81 

Oxygen, sulphur, and phosphorus 21-84 22-29 

100-00 10000 

1 Liebig, Ann. der Chem. und Pharm. xxxix. 129. 



520 ANIMAL NUTRITION. 

The composition of vegetable casein, or legumin, has not been so well ma<1a 
out ; so much discrepancy appears in the analyses as to lead to the suppo- 
sition that different substances have been operated upon. 

The great bulk, however, of the solid portion of the food of the herbivora 
consists of bodies which do not contain nitrogen, and therefore cannot yield 
sustenance in the manner described : some of these, as vegetable fibre or lig- 
nin, and waxy matter, pass unaltered through the alimentary canal ; others, 
as starch, sugar, gum, and perhaps vegetable fat, are absorbed into the sys- 
tem, and afterwards disappear entirely: they are supposed to contribute 
very largely to the production of animal heat. 

On these principles, Professor Liebig 1 has very ingeniously made the dis- 
tinction between what he terms plastic elements of nutrition and elements of 
respiration ; to the former class belong 

Vegetable fibrin, 
Vegetable albumin, 
Vegetable casein, 
Animal flesh, 
Blood. 



To the latter, 
Fat, 
Starch, 
Gum, 
Cane-sugar, 



Grape-sugar, 
Milk-sugar, 
Pectine, 
Alcohol ? 



In a flesh-eating animal the waste of the tissues is very rapid, the tem- 
perature being, as it were, kept up in great measure by the burning of 
azotized matter ; in a vegetable feeder it is probably not so great, the non- 
azotized substances being consumed in the blood in the place of the organic 
fabric. 

When the muscular movements of a healthy animal are restrained, a genial 
temperature kept up, and an ample supply of food containing much amyla- 
ceous or oily matter given, an accumulation of fat in the system rapidly takes 
place ; this is well-seen in the case of stall-fed cattle. On the other hand, 
when food is deficient, and much exercise is taken, emaciation results. These 
effects are ascribed to difference in the activity of the respiratory function ; 
in the first instance, the heat-food is supplied faster than it is consumed, and 
hence accumulates in the form of fat; in the second, the conditions are re- 
versed, and the creature is kept in a state of leanness by its rapid con- 
sumption. The fat of an animal appears to be a provision of nature for the 
maintenance of life during a certain period under circumstances of privation. 

The origin of fat in the animal body has recently been made the subject 
of much animated discussion ; on the one hand it was contended that satis- 
factory evidence exists of the conversion of starch and saccharine substances 
into fat, by separation of carbon and oxygen, the change somewhat resem- 
bling that of vinous fermentation : it was argued, on the other side, that oily 
or fatty matter is invariably present in the food supplied to the domestic ani- 
mals, and that this fat is merely absorbed and deposited in the body in a 
slightly modified state. The question has now been decided in favour of the 
first of these views, which was enunciated by Professor Liebig, by the very 
chemist who formerly advocated the second opinion. By a series of very 
beautiful experiments, MM. Dumas and Milne Edwards proved that bees 
exclusively feeding upon sugar were still capable of producing wax, which 
was pointed out as a veritable fact. 

1 Animal Chemistry, p. 96. 



ANIMAL NUTRITION. 521 

It is not known in what manner digestion, the reduction in the stomach of 
the food to a nearly fluid condition, is performed. The natural secretion of 
that organ, the gastric juice, is said to contain a very notable quantity of free 
hydrochloric acid. Dilute hydrochloric acid, aided by a temperature of 98° 
(36°-6C) or 100° (37° -7C), dissolves coagulated albumin, fibrin, &c. ; but 
many hours are required for that purpose. The gastric secretion has been 
supposed to contain a peculiar organic principle called pepsin, said to have 
been isolated, to which this power of dissolving albuminous substances in 
conjunction with the hydrochloric acid is attributed. In the saliva a pecu- 
liar organic principle exists, which causes the conversion of starch into sugar. 
If starch is held in the mouth even for two minutes, this change is found to 
occur. The active cause of this change has been looked on as a kind of ani- 
mal diastase. 

The food of animals, or rather that portion of the food which is destined 
to the repair and renewal of the frame itself, is thus seen to consist of sub- 
stances identical in composition with the body it is to nourish, or requiring 
but little chemical change to become so. 

The chemical phenomena observed in the animal system resemble so far 
those produced out of the body by artificial means, that they are all, or nearly 
all, so far as is known, changes in a descending series ; albumin and fibrin 
are probably more complex compounds than gelatin or the membrane which 
furnishes it; this, in turn, has a far greater complexity of constitution than 
urea, the regular form in which rejected azotized matter is conveyed out of 
the body. The animal lives by the assimilation into its own substance of the 
most complex and elaborate products of the organic kingdom ; — products 
which are, and, apparently, can only be, formed under the influence of vege- 
table life. 

The existence of the plant is maintained in a manner strikingly dissimilar: 
the food supplied to vegetables is wholly inorganic ; the carbonic acid and 
nitrogen of the atmosphere, the water which falls as rain, or is deposited as 
dew; the minute trace of ammoniacal vapour present in the air; the alkali 
and saline matter extracted from the soil; — such are the substances which 
yield to plants the elements of their growth. That green healthy vegetables 
do possess, under circumstances to be mentioned immediately, the property 
of decomposing carbonic acid absorbed by their leaves from the air, or con- 
veyed thither in solution through the medium of their roots, is a fact posi- 
tively proved by direct experiment, and rendered certain by considerations 
of a very stringent kind. To effect this very remarkable decomposition, the 
influence of light is indispensable; the diffuse light of day suffices in some 
degrees, but the direct rays of the sun greatly exalt the activity of the pro- 
cess. The carbon separated in this manner is retained in the plant in union 
with the elements of water, with which nitrogen is also sometimes associated, 
while the oxygen is throw n off into the air from the leaves in a pure and 
gaseous condition. 

The effect of ammoniacal salts upon the growth of plants is so remarkable, 
as to leave little room for doubt concerning the peculiar function of the am- 
monia recently discovered in the air. Plants which in their cultivated state 
contain, and consequently require, a large supply of nitrogen, as wheat, and 
the cereals in general, are found to be greatly benefited by the application 
to the land of such substances as putrefied urine, which may be looked upon 
as a solution of carbonate of ammonia, the guano 1 of the South Seas, which 

1 Guano is the partially decomposed dung of birds, found in immense quantity on some 
of the barren islets of the western coast of South America, as that of Peru. More recently, 
similar deposits have been found on the coast of Southern Africa. The guano now imported 
into England from these localities is usually a soft, brown powder, of various shades of 
colour. White specks of bone-earth, and sometimes masses of saline matter, may be found 
44* 



522 VEGETABLE NUTRITION. 

usually contains a large proportion of ammoniacal salt, acd even of a pure 
sulphate of ammonia. Some of these manures doubtless owe a part of their 
value to the phosphates and alkaline salts they contain; still, the chief effect 
is certainly due to the ammonia. 

Upon the members of the vegetable kingdom thus devolves the duty of 
building up, as it were, out of the inorganic constituents of the atmosphere, 
— the carbonic acid, the water, and the ammonia, — the numerous complicated 
organic principles of the perfect plant, many of which are afterwards des- 
tined to become the food of animals, and of man. The chemistry of vege- 
table life is of a very high and mysterious order, and the glimpses occasion- 
ally obtained of its general nature are few and rare. One thing, however, 
is manifest, namely, the wonderful relations between the two orders of or- 
ganized beings, in virtue of which the rejected and refuse matter of the one 
is made to constitute the essential and indispensable food of the other. 
While the animal lives, it exhales incessantly from its lungs, and often from 
its skin, carbonic acid ; when it dies, the soft parts of its body undergo a 
series of chemical changes of degradation, which terminate in the production 
of carbonic acid, water, carbonate of ammonia, and, perhaps, other products 
in small quantity. These are taken up by a fresh generation of plants, 
which may in their turn serve for food to another race of animals. 

in it. That which is most recent, and probably most valuable as manure, often contains un- 
decomposed uric acid, besides much oxalate or hydrochlorate of ammonia, and alkaline phos- 
phates, and other salts: it has a most offensive odour. The specimens taken from oldei 
deposits have but little smell, are darker in colour, contain no uric acid, and much less am- 
moniacal salt; the chief components are bone «art,h, a peculiar dark-coloured organic matter, 
and soluble inorganic salts. See also page 443. 



SUB -STANCES OBTAINED FROM TAR. 523 



SECTION IX. 

ON CERTAIN PRODUCTS OF THE DESTRUCTIVE DISTILLATION 
AND SLOW PUTREFACTIVE CHANGE OF ORGANIC MATTER. 



SUBSTANCES OBTAINED FROM TAR. 

There are three principal varieties of tar: — (1.) Tar of the wood-vinegar 
maker, procured by the destructive distillation of dry hard wood ; (2.) 
Stockholm tar, so largely consumed in the arts, as in ship-building, &c, 
■which is obtained by exposing to a kind of rude distillatio per descensum tho 
roots and useless parts of resinous pine and fir-timber; and, lastly, (3.) 
Coal or mineral tar, a by-product in the manufacture of coal-gas. This is 
viscid, black, and ammoniacal. 

All these tars yield by distillation, alone or with water, oily liquids of 
extremely complicated nature, from which a number of curious products, to 
be presently described, have been procured; the solid brown or black resi- 
due constitutes pitch. Hard-wood tar furnishes the following : — 

Paraffin ; tar-oil stearin. — This remarkable substance is found in 
that part of the wood-oil which is heavier than water ; it is extracted by re- 
distilling the oil in a retort, collecting apart the last portions, gradually 
adding a quantity of alcohol, and exposing the whole to a low temperature. 
Thus obtained, paraffin appears in the shape of small, colourless needles, 
fusible at 110° (43° -3C) to a clear liquid, -which on solidifying becomes 
glassy and transparent. It is tasteless and inodorous ; volatile without 
decomposition; and burns, when strongly heated, with a luminous yet 
smoky flame. It is quite insoluble in water, slightly soluble in alcohol, 
freely in ether, and miscible in all proportions, when melted, with both fixed 
and volatile oils. The most energetic chemical reagents, as strong acids, 
alkalis, chlorine, &c, fail to exert the smallest action on this substance; it 
is not known to combine in a definite manner with any other body, whence 
its extraordinary name, from parum affinis. 

Paraffin contains carbon and hydrogen only, and in the same proportions 
as in defiant gas, or CH. M. Lewy, of Copenhagen, makes it C 20 H 21 . The 
rational formula is unknown. 

Eupione.' — This is the chief component of the light oil of wood-tar; i* 
occurs also in the tar of animal matters, and in the fluid product of the dis- 
tillation of rape-seed oil. Its separation is effected by the agency of concen- 
trated sulphuric acid, or of a mixture of sulphui'ic acid and nitre, which 
oxidizes and destroys most of the accompanying substances. In a pure 
state, it is an exceedingly thin, colourless liquid, of agreeable aromatic 
odour, but destitute of taste ; it is the lightest known liquid, having a den- 
sity of G55. At 116° (46°6C) it boils and distils unchanged. Dropped 
upon paper, it makes a greasy stain, which after a time disappears. Eupione 
is very inflammable, and burns with a bright luminous flame. In water it is 



From tu, good, beautiful, and tziov. fat. 



524 SUBSTANCES OBTAINED FROM TAR. 

quite insoluble, in rectified spirit nearly so, but "with ether and oils freely 
miscible. 

Eupione is a hydrocarbon ; according to M. Hess it consists of C 5 II 6 . It 
is very probable that eupione frequently contains and sometimes entirely 
consists of hydride of amyl (see page 389). 

Other volatile oils, having a similar origin, and perhaps a similar compo- 
sition, but differing from the above in specific gravity and boiling-point, are 
sometimes confounded with eupione. The study of these substances presents 
many serious difficulties. It is even doubtful -whether the eupione be not 
formed by the energetic chemical agents employed in its supposed purifica- 
tion, and this remark applies with even greater force to the next three or 
four tar-products to be noticed. 

Picamar. 1 — A component of the heavy oil of wood ; it is a viscid, colour- 
less, oily liquid, of feeble odour, but intensely bitter taste. Its density is 
1-095, and it boils at 518° (270°C). It is insoluble in water, but dissolves 
in all proportions in alcohol, ether, and the oils. The most characteristic 
property of picamar is that of forming with the alkalis and ammonia crys- 
talline compounds, which, although decomposed by water, are soluble with- 
out change in spirit. The composition of this substance is unknown. 

Kapnomor. 2 — Such is the name given by Dr. Reichenbach to another oily 
liquid obtained from the same source as the last, by a long and complex 
process, in which strong solutions of caustic potassa are freely used. It is 
described as a colourless volatile oil, of high boiling-point, and rather lighter 
than water ; it has an odour of ginger, and a taste feeble at first, but after- 
wards becoming connected with an insupportable sense of suffocation. 
Water refuses to dissolve it ; alcohol and ether take it up easily ; and oil 
of vitriol combines with it, giving rise to a complex acid, the potassa-salt of 
which is crystallizable. Its composition is unknown. 

Cedriret. 3 — The lighter oil of hard-wood tar contains a substance, separ- 
able from the eupione, &c, by caustic alkalis, which in contact with oxidizing 
agents, as sulphate of sesquioxide of iron, chromic acid, or even atmos- 
pheric air, yields a mass of small, red, reticulated crystals, infusible by 
heat, and soluble in concentrated sulphuric acid with deep indigo-blue 
colour. This substance is insoluble in water, alcohol, and ether ; nothing is 
known respecting its composition. 

Kreosote. 4 — This is by far the most important and interesting body of 
the group ; its discovery is due to Dr. Pteichenbach ; it is the principle to 
which wood-smoke owes its power of curing and preserving salted meat and 
other provisions. Kreosote is most abundantly contained in the heavy oil 
of beech-tar, as procured from the wood-vinegar maker, and is thence ex- 
tracted by a most tedious and complicated series of operations ; it certainly 
pre-exists, however, in the original material. The tar is distilled in a me- 
tallic vessel, and the different products collected apart ; the most volatile 
portion, which is lighter than water, and consists chiefly of eupione, is re- 
jected ; the second portion is denser, and contains the ki*eosote, and is set 
aside ; the distillation is stopped when paraffin begins to pass over in quan- 
tity. The impure kreosote is first agitated with carbonate of potassa to 
remove adhering acid, separated, and re-distilled, the first part being again 
rejected ; it is next strongly shaken with a solution of phosphoric acid, and 
again distilled ; a quantity of ammonia is thus separated. Afterwards, it is 
dissolved in a solution of caustic potassa of specific gravity 1-12, and de- 

1 From p;a;, and amarus, in allusion to its bitter taste. 

a From /carros, smoke, fxoipa, part. 

3 From cedrium, the old name for acid tar-water, and rete,, a net. 

* Derived from xpias, flesh, and o-«£u>, I preserve. 



SUBSTANCES OBTAINED FROM TAR. 525 

canted from the insoluble oil which floats on the surface ; this alkaline liquid 
is boiled, and left some time in contact with air, by which it acquires a brown 
colour from the oxidation of some yet unknown substance present in the 
crude product. The compound of kreosote and alkali is next decomposed 
by sulphuric acid ; the separated kreosote is again dissolved in caustic 
potassa, boiled in the air, and the solution decomposed by acid, and this 
treatment repeated until the product ceases to become coloured by the joint 
influence of oxygen and the alkaline base. When so far purified, it is well 
washed with water, and distilled. The first portion contains water; that 
which succeeds is pure kreosote. 

In this condition kreosote is a colourless, somewhat viscid oily liquid, of 
great refractive and dispersive power. It is quite neutral to test-paper ; it 
has a penetrating and most peculiar odour, that, namely, of smoked meat, 
and a pungent and almost insupportable taste when placed in a very small 
quantity upon the tongue. The density of this substance is 1-037, and its 
boiling-point 397° (202°-8C). It inflames with difficulty, and then burns 
with a smoky light. When quite pure, it is inalterable by exposure to the 
air; much of the kreosote of commerce becomes, however, under these cir- 
cumstances, gradually brown. 100 parts of cold water take up about \\ 
parts of kreosote ; at a high temperature rather more is dissolved, and the 
hot solution abandons a portion on cooling. The kreosote itself absorbs 
water also to a considerable extent. In acetic acid it dissolves in much 
larger quantity. Alcohol and ether mix with kreosote in all proportions. 
Concentrated sulphuric acid, by the aid of heat, blackens and destroys it. 
Caustic potassa dissolves kreosote with great facility, and forms with it a 
definite compound, which crystallizes in brilliant pearly scales. 

Kreosote consists of carbon, hydrogen, and oxygen, but its exact compo- 
sition is yet uncertain. The formula C 14 H 8 2 has been given. 

The most remarkable and characteristic feature of the compound in ques- 
tion is its extraordinary antiseptic power. A piece of animal flesh steeped 
in a very dilute solution of kreosote dries up to a mummy-like substance, 
but absolutely refuses to putrefy. The well-known efficacy of impure wood- 
vinegar in preserving provisions is with justice attributed to the kreosote it 
contains ; and the effect of mere wood-smoke is also thus explained. In a 
pure state, kreosote is sometimes employed by the dentist for relieving tooth- 
ache arising from putrefactive decay in the substance of the tooth. 

Chrysen and pyren. — M. Laurent extracted from pitch, by distillation 
at a high temperature, two new solid bodies, to which he gave the preceding 
nanaes; they condense together, with a quantity of oily matter, partly in the 
neck of the retort, and partly in the receiver, and are separated by the aid 
of ether. Chrysen, so called from its golden colour, is a pure yellow, crystal- 
line powder, which fuses by heat,. and sublimes without much decomposition. 
It is insoluble in water and alcohol, and nearly insoluble in ether : warm oil 
of vitriol dissolves it, with the development of a beautiful deep-green colour. 
Boiling nitric acid converts it into an insoluble red substance, which has not 
been studied. Chrysen is composed of C 3 H. 

Pyren differs from the preceding substance in being colourless, crystal- 
lizing in small, soft, micaceous scales, soluble in boiling alcohol and ether. 
It is fusible and volatile. Pyren contains C 5 H 2 . 

Oil of ordinary tar, obtained by distillation alone, or with water, consists 
in great measure of unaltered oil of turpentin, mixed, however, with em- 
pyreumatic oily products, which give it a powerful odour and a dark colour 
The residual pitch contains much pine-resin, and thus differs from the solid 
portion of the hard wood-tar so frequently mentioned. 



526 VOLATILE PRINCIPLES OF COAL-TAR. 

Volatile Principles of Coal-Tar . 

Coal-tar yields on distillation a large quantity of thin, dark-coloured, 
volatile oil, which, when agitated with dilute sulphuric acid to remove am- 
monia, and twice rectified with water, becomes nearly colourless : it is very 
volatile, lighter than water, very inflammable, and possesses in a high degree 
the property of dissolving caoutchouc, on which account it is very exten- 
sively used in the manufacture of water-proof fabrics containing that 
material. 

This coal-oil is a mixture of a great variety of liquids and solids dissolved 
in the oil. By the action of acids and alkalis, this mixture may be conve- 
niently divided into three separate groups. (1) A group of basic compounds 
soluble in acids; (2) an acid portion soluble in alkalis; and (3) a group of 
neutral constituents. 

The basic constituents form but a small part of coal-tar-oil. They are ex- 
tracted by agitating successively large quantities of the oil with hydrochloric 
acid, and afterwards distilling the acid watery liquid obtained with excess 
of hydrate of lime. The bases thus obtained consist chiefly of picoline (see 
page 465), aniline (see page 459), and leucoline (see page 464), and are 
separated by distillation ; these three compounds boiling at very different 
temperatures. 

The acid portion of coal-tar-oil consists essentially of carbolic acid or 
phenol. 

Carbolic acid ; phenol. — Common coal-tar-oil is agitated with a mixture 
of hydrate of lime and water, the whole being left for a considerable time ; 
the aqueous liquid is then separated from the undissolved oil, decomposed 
by hydrochloric acid, and the oily product obtained purified by cautious dis- 
tillation, the first third only being collected. Or crude coal-oil is subjected 
to distillation in a retort furnished with a thermometer, and the portion 
which passes over between the temperatures of 300° — 400° (149° — 204°-5C) 
collected apart. This product is then mixed with a hot strong solution of 
caustic potassa, and left to stand; a whitish, somewhat crystalline, pasty 
mass is obtained, which by the action of water is resolved into a light oily 
liquid and a dense alkaline solution. The latter is withdrawn by a syphon, 
decomposed by hydrochloric acid, and the separated oil purified by contact 
with chloride of calcium and re-distillation. Lastly, it is exposed to a low 
temperature, and the crystals formed drained from the mother-liquor and 
carefully preserved from the air. 

Pure carbolic acid forms long colourless prismatic needles, which melt at 
95° (35°C) to an oily liquid, boiling at 370° (180°C), and greatly resembling 
kreosote 1 in many particulars, having a very penetrating odour and burning 
taste, and attacking the skin of the lips. Its sp. gr. is 1-065. It is slightly 
soluble in water, freely in alcohol and ether, and has no acid reaction to 
test-paper. The crystals absorb moisture with avidity, and liquefy. It co- 
agulates albumin. Sulphur and iodine dissolve in it ; nitric acid, chlorine, 
and bromine attack it with energy. Carbolic acid contains C, 2 H 6 0,HO. 

In its chemical deportment carbolic acid stands very near the alcohols, a 
fact to which allusion has been made already in former sections (see pages 
399 and 401) ; we may assume in it a compound radical, phenyl, C 12 TT 5 =Pyl, 
analogous to ethyl, when carbolic acid becomes Pyl 0,110, or hydrated oxide 
mi phenyl. 

With sulphuric acid, hydrate of oxide of phenyl forms the compound acid, 



A great deal of the kreosote which occurs in commerce is, in fact, nothing but more or 
less pure carbolic acid. 



VOLATILE PRINCIPLES OF COAL-TAR. 527 

etate in the dry vacuum. This acid closely corresponds to sulphovinic acid 
(see page 358). The baryta-salt crystallizes from alcohol in minute needles. 
Phenyl-alcohol dissolves potassium with evolution of hydrogen, a com- 
pound C 12 H 5 0,KO being produced, which is analogous to the substance formed 
in a similar manner from common alcohol (see page 347). On heating this 
potassa-compound with iodide of methyl, ethyl, or amyl, a series of double 
ethers are produced represented by the following formulae : — 

Oxide of phenyl and methyl PylO,MeO = C 12 rI 5 0,C 2 H 3 = C M TT s 2 

Oxide of phenyl and ethyl PylO,AeO = C 12 H 5 0,C 4 H 5 = C ]6 H 10 O 2 

Oxide of phenyl and amyl PylO,AyO = C 12 H 5 O,C, H n O = C n ll 16 2 

Those substances also described by the names anisol (because it is likewise 
produced by the distillation of anisic acid (see page 491), phenetol and phe- 
namylol are evidently analogous to the compounds of oxide of methyl with 
those of ethyl and amyl, which have been mentioned in pages 382 and 389. 

A chloride of phenyl, C 12 H 5 Cl=PylCl, has been produced by the action of 
pentachloride of phosphorus upon hydrated oxide of phenyl. This com- 
pound, however, which is a heavy oil, is but very imperfectly known. 

Cyanide of phenyl, C, 4 H 5 N==C 12 H 5 C 2 N=PylCy, has not yet been produced 
from phenyl-alcohol directly. The substance, however, which has been de- 
scribed under the name of benzonitrile (page 401), is both by composition 
and deportment cyanide of 'phenyl, perfectly analogous to cyanide of ethyl 
(see page 354). Boiled with potassa it is converted into ammonia and ben- 
zoic acid, cyanide of ethyl furnishing ammonia and propionic acid. Starting 
from this decomposition, benzoic acid may be viewed as phenyl-oxalic acid 
C 14 H 5 3 .HO = Ci 2 H 5 ,C 2 3 ,HO, just as propionic acid may be regarded as 
ethyl-oxalic acid (see page 392). 

Hydrated oxide of phenyl when treated with chloride of benzoyl (see page 
400) yields hydrochloric acid and a white fusible crystalline compound which 
is benzo ate of phenyl C 12 H 5 0,C 14 H 5 3 — PylO,BzO, analogous to benzoate of 
ethyl; when heated wi-h ammonia, phenyl-alcohol yields aniline C ]2 H 7 N — 
C 12 H 5 H 2 N=PylH 2 N (phenylamine), the ethylamine of the phenyl-series (see 
page 459). 

The following table gives a synopsis of the phenyl-compounds, which have 
been placed in juxtaposition with the corresponding terms of the ethyl- 
series : — 

Phenyl-alcohol PylO,HO AeO,HO Ethyl-alcohol 

OX pot e as sl Phenyl " } P ^,KO AeO,KO Oxide of ethyl-potassa 

Sulphophenic acid PylO,2S0 3 ,HO AeO,2S0 3 ,HO Sulphovinic acid 

AeO Oxide of ethyl 

Chloride of phenyl PylCl(?) Aecl Chloride of ethyl 

Cyanide of phenyl 1 PvlP _ . r _ / Cyanide of ethyl (pro- 

(benzonitrile) J ***"* Ae ^ \ pio nitrile) 

Benzoate of phenyl PylO,PylC 2 3 AeO,Ae,C 2 3 Propionate of ethyl 

Phenyl-amine (ani- ~| ^t TT -n -, , TTT . t,., , 

lin ^ * J-MT 2 Pyl NH 2 Ae Ethylamine 

Thenyl-urea C 2 (H 3 Pyl)N0 2 C 2 (H 3 Ae)N0 2 Ethyl-urea. 

Chlorophenisic acid. — This is the characteristic and principal product of 
the action of chlorine on hydrate of oxide of phenyl. The pure substance 
is not necessary for the preparation of this body, those portions of crude 
coal-oil which boil between 360° — 400° (182° -2 — 204°-5C) answering very 
well. The oil is saturated with chlorine, and distilled in the open air, the 
first and last portions being rejected; the product is again treated with 



528 VOLATILE PRINCIPLES OF COAL-TAR. 

chlorine until the whole solidifies. The crystals are drained and dissolved 
in hot dilute solution of ammonia ; on cooling, the sparingly soluble chloro- 
phenisate of ammonia crystallizes out. This is dissolved in pure water, de- 
composed by hydrochloric acid, washed, and, lastly, distilled. 

Chlorophenisic acid forms exceedingly fine, colourless, silky needles, which 
melt when gently heated ; it has a very penetrating, persistent, and charac- 
teristic odour, is very sparingly soluble in water, but dissolves freely in 
alcohol, ether, and hot concentrated sulphuric acid. It slowly sublimes at 
common temperatures, and distils with ebullition when strongly heated. 
Chlorophenisic acid forms well-defined salts, and contains C 12 (H 2 C1 3 )0,H0. 
By the action of a great excess of chlorine an analogous acid richer in chlo- 
rine is formed. It is called chlorophenusic acid, and contains C l2 Cl 5 0,HO. 
Brorioophenisic acid is prepared by analogous means, and possesses a consti- 
tution and character greatly resembling those of the chlorine-compound. 

Nitrophenasic acid. — On distilling phenyl-alcohol with very dilute nitric 
acid, beautiful yellow needles are obtained, soluble in ammonia and potassa, 
and yielding a beautiful red silver-salt. This substance is nitrophenasic acid, 
C 12 H 4 N0 5 ,HO = C ]2 (R 4 N0 4 )0,HO. Nitrophenesic and nitrophenisic acids may 
be prepared directly from the oil which is employed in the preparation of 
chlorophenisic acid. The oil is carefully mixed in a large open vessel with 
rather more than its own weight of ordinary nitric acid. The action is very 
violent. The brownish-red substance produced is slightly washed with 
water, then boiled with dilute ammonia, and filtered hot. A brown mass 
remains on the filter, which is preserved to prepare nitrophenisic acid, and 
the solution deposits on cooling a very impure ammoniacal salt of nitro- 
phenesic acid, which requires several successive crystallizations, after which 
it is decomposed by nitric acid and the product crystallized from alcohol. 

Nitrophenesic acid forms blonde-coloured prismatic crystals, very spar- 
ingly soluble even in boiling water, but freely soluble in alcohol. It has no 
odour. Its taste, at first feeble, becomes after a short time very bitter. At 
219° (104°C) it melts, and on cooling crystallizes. In very small quantity 
it may be distilled without decomposition, but when briskly heated it often 
detonates, but not violently. The salts of this acid are yellow or orange 
and very beautiful : they are mostly soluble in water, and detonate feebly 
when heated. The acid contains Cj2H 3 N 2 9 ,HO = C 12 H 3 (N0 4 ) 2 0,HO. Nitro- 
phenisic acid is identical with picric or carbazotic acid (see page 473). It 
may be prepared with great economy from impure nitrophenesic acid, or 
from the brown mass insoluble in dilute ammonia already referred to. It is 
purified by a process similar to that employed in the case of the preceding 
substances. Nitrophenisic acid contains C 12 H 2 N 3 13 ,HO=Ci 2 H 2 (N0 4 ) 5 0,H0. 1 

The following table exhibits the relation of these substitution-products : — 

Phenyl-alcohol C, 2 H 5 0,110 = Phenol 

Chlorophenisic acid C ]2 (H 2 C1 3 ) 0,HO = Trichlorophenol 

Nitrophenasic acid C 12 (H 4 N0 4 ) 0,HO = Nitrophenol 
Nitrophenesic acid C 12 (H 3 [N0 4 ] 2 ) 0,HO = Binitrophenol 
Nitrophenisic acid C 12 (H 2 [N0 4 ] 3 ) 0,H0 = Trinitrophenol. 

The neutral portion of coal-tar naphtha consists of a great variety of hy- 
drocarbons, partly liquid, partly solid. The liquid hydrocarbons have been 
already described (see pages 398 and 403). They are chiefly benzol, toluol, 
xylol, cumol, and cymol? The solid hydrocarbons are naphthalin and par a- 
naphihalin together with several similar substances less perfectly known. 

1 Ann. Cbim. ct Phys. 3d series, iii. 195. 

a The same hydrocarbons have been lately found by M. Cahours in the oily liquids pre 
ripitated by water from commercial wood-spirits (see page 387). 



VOLATILE PRINCIPLES OF COAL-TAR. 529 

Naphthalin. — When, in the distillation of coal-tar, the last portion of 
the volatile oily product is collected apart and left to stand, a quantity of 
solid, crystalline matter separates, -which is principally composed of the 
substance in question. An additional quantity may be obtained by pushing 
the distillation until the contents of the vessel begin to char ; the naphthalin 
then condenses in the solid state, but dai*k-coloured and very impure. By 
simple sublimation, once or twice repeated, it is obtained perfectly white. 
In this state naphthalin forms large, colourless, transparent, brilliant, crys- 
talline plates, exhaling a faint and peculiar odour, -which has been compared 
to that of the narcissus. Naphthalin melts at 176° (80°C) to a clear, colour- 
less liquid, -which crystallizes on cooling; it boils at 413° (211°-6C), and 
evolves a vapour whose density is 4-528. When strongly heated in the air, 
it inflames and burns with a red and very smoky light. It is insoluble in 
cold water, but soluble to a slight degree at the boiling temperature ; alcohol 
and ether dissolve it easily ; a hot saturated alcoholic solution deposits fine 
iridescent crystals on cooling. 

Naphthalin is found by analysis to contain C^H^ or C 20 H 8 . 

Naphthalin dissolves in warm concentrated sulphuric acid, forming a red 
liquid, which, when diluted with water, and saturated with carbonate of 
baryta, yields salts of at least two distinct acids, analogous to sulphovinic 
acid. One of these, the sulphonaphthalic acid of Mr. Faraday, crystallizes 
from a hot aqueous solution in small white scales, which are but sparingly 
soluble in the acid. The free acid is obtained in the usual manner by de- 
composing the baryta-salt with sulphuric acid ; it forms a colourless, crys- 
talline, brittle mass, of acid, metallic taste, very deliquescent, and very solu- 
ble in water. The second baryta-salt is still less soluble than the preceding. 
The composition of sulphonaphthalic acid is C 20 H 7 S 2 O 5 ,HO. 

Fuming nitric acid at a high temperature attacks naphthalin ; the products 
are numerous, and have been attentively studied by M. Laurent. The same 
chemist has described a long series of curious products of the action of chlo- 
rine on naphthalin. Nitric acid gives rise to a great number of nitro-sub- 
stitutes, the most interesting of which, is the compound known by the name 
nitronaphthala.se, which, when submitted to Zinin's process, is converted into 
naphthalidine (see page 462). Among the derivatives of naphthalin, a com- 
pound deserves to be mentioned, which has been described under the name 
of phthalic acid. This acid has not yet been produced directly from naphtha- 
lin, but may be obtained by boiling one of the products of the action of chlo- 
rine upon naphthalin, namely, the tetrachloride of naphthalin (C 20 H 8 C1 4 ) 
with nitric acid. The same substance is formed by submitting alizarin to the 
action of nitric acid. 

Phthalic acid crystallizes in yellow plates ; it is biit slightly soluble in cold 
water, but dissolves freely in alcohol and ether. Phthalic acid is bibasic, and 
contains C 16 H 4 6 ,2HO; when heated it loses 2 eq. of water, and becomes 
C 1G H 4 6 . Treated with fuming nitric acid it yields a nitro-acid, nitro-phtha- 
lic acid, C 16 (H 3 N0 4 ) 6 , 2HO. When distilled with baryta it is converted into 
benzol : — 

C ]6 H 6 8 -f4BaO = 4(BaOCG,)-f-C I2 H 6 

Phthalic acid. Benzol. 

The formation of phthalic acid from alizarin has established a most inte- 
resting connection between the naphthalin and alizarin-series. It would be 
of great interest if naphthalin, which is produced xii enormous quantities in 
the manufacture of coal-gas, but has not yet found any useful application, 
could be converted by chemical processes into alizarin. That there is a hope 
of such a conversion being possible, is even now pointed out by the close 
45 



530 

analogy af one of the chlorine products of naphthalin, of chloronaphihalu 
acid, both in composition and properties with alizarin. This substance con- 
tains C 20 (H 5 C1)0 6 , and may be viewed as chloralizarin : — 



Cloronaphthalic acid C 20 (H 5 Cl)O 6 . 

Chloronaphthalic acid produces most beautifully coloured compounds with 
the metallic oxides. 

The history of the formation of naphthalin is rather interesting ; it is per- 
haps the most stable of all the more complex compounds of carbon and hydro- 
gen : in a vessel void of free oxygen it may be heated to any extent without 
decomposition ; and. indeed, where other carburets of hydrogen are exposed 
to a very high temperature, as by passing in vapour through a red-hot 
porcelain tube, a certain quantity of naphthalin is almost invariably pro- 
duced. Hence its presence in coal and other tar is mainly dependent upon 
the temperature at which the destructive distillation of the organic substance 
has been conducted. Lampblack very frequently contains naphthalin thus 
accidentally produced. 

Paranaphthalin. — This substance occurs in the naphthalin of coal-tar, 
and is separated by the use of alcohol, in which ordinary naphthalin is freely 
soluble, whilst paranaphthalin is almost totally insoluble ; in other respects 
it much resembles naphthalin. "The crystals obtained by sublimation are, 
however, usually smaller and less distinct. It melts at 356° (180°C), and 
boils at 570° (299°C), or above. Its best solvent is oil of turpentin. Para- 
naphthalin has the same composition as naphthalin itself; the density of its 
vapour is, however, different, viz., 6-741. Its composition may be repre- 
sented by the formula C 30 H 12 . 

PETROLEUM, NAPHTHA, AND OTHER ALLIED SUBSTANCES. 

Pit-coal, lignite or broim coal, jet, bitumen of various kinds, petroleum or 
rock-oil, and naphtha, and a few other allied substances more rarely met with, 
are looked upon as products of the* decomposition of organic matter, espe- 
cially vegetable matter, beneath the surface of the earth, in situations where 
the conditions of contact with water, and nearly total exclusion of atmo- 
spheric air, are fulfilled. Deposited at the bottom of seas, lakes, or rivers, 
and subsequently covered up by accumulations of clay and sand, hereafter 
destined to become shale and gritstone, the organic tissue undergoes a kind 
of fermentation, by which the bodies in question, or certain of them, are 
slowly produced. Carbonic acid and light carbonetted hydrogen are by-pro- 
ducts of the reaction ; hence their frequent disengagement, the first from 
beds of lignite, and the second from the farther advanced and more perfect 
coal. 

The vegetable origin of coal has been placed beyond doubt by microscopic 
research ; vegetable structure can be thus detected even in the most mas- 
sive and perfect varieties of coal when cut into thin slices. In coal of infe- 
rior quality, much mixed with earthy matter, it is evident to the eye ; the 
leaves of ferns, reeds, and other succulent plants, more or less resembling 
those of the tropics, are found in a compressed state between the layers of 
shale or slaty clay, preserved in the most beautiful manner, but entirely 
converted into bituminous coal. The coal-mines of Europe, and particularly 
those of our own country, furnish an almost complete fossil-flora ; a history 
of many of the now lost species which once decorated the surface of the 
earth. 

In the lignites the woody structure is much more obvious. Beds of this 
material are found in very many of the newer strata, above the true coal, to 
which they are consequently posterior. As an article of fuel, brown-coal is 



AND OTHER ALLIED SUBSTANCES. 531 

of comparatively small value ; it resembles peat, giving but little flame and 
emitting a disagreeable, pungent smell. 

Jet, used for making black ornaments, is a variety of lignite. 

The true bitumens are destitute of all organic structure ; they appear to 
have arisen from coal or lignite by the action of subterranean heat, and 
very closely resemble some of the products yielded by the destructive dis- 
tillation of those bodies. They are very numerous, and have yet been but 
imperfectly studied. 

1. Mineral pitch, or compact bitumen, the asphaltum or Jew's pitch of some 
authors. — This substance occurs abundantly in many parts of the world; 
as, in the neighbourhood of the Dead Sea in Judea ; in Trinidad, in the 
famous pitch lake, and elsewhere. It generally resembles in aspect common 
pitch, being a little heavier than water, easily melted, very inflammable, and 
burning with a red, smoky flame. It consists principally of a substance 
called by M. Boussingault asphaltene, composed of C 20 H 16 O 3 .~ It is worthy 
of remark, that M. Laurent found paranaphthalin in a native mineral 
pitch. 

2. Mineral tar seems to be essentially a solution of asphaltene in an oily 
fluid called petrolene. This has a pale yellow colour and peculiar odour ; it 
is lighter than water, very combustible, and has a high boiling point. It 
has the same composition as the oils of turpentin and lemon-peel, namely 
C 10 H 8 . Asphaltene contains, consequent, the elements of petrolene, to- 
gether with a quantity of oxygen, and probably arises from the oxidation of 
that substance. 

3. Elastic bitumen ; mineral caoutchouc. — This curious substance has only 
been found in three places ; in a lead-mine at Castleton, in Derbyshire ; at 
Montrelais, in France ; and in the State of Massachusetts. In the two latter 
localities it occurs in the coal-series. It is fusible, and resembles in many 
respects the other bitumens. 

Under the names petroleum and naphtha are arranged various mineral oils 
which are observed in many places to issue from the earth, often in con- 
siderable abundance. There is every reason to suppose that these owe their 
origin to the action of internal heat upon beds of coal, as they are usually 
found in connection with such. The term naphtha is given to the thinner 
and purer varieties of rock-oil, which are sometimes nearly colourless ; the 
darker and more viscid liquids bear the name of petroleum. 

Some of the most noted localities of these substances are the following : — 
The north-west side of the Caspian Sea, near Baku, where beds of marl are 
found saturated with naphtha. Wells are sunk to the depth of about 30 
feet, in which naphtha and water collect, and are easily separated. In some 
parts of this district so much combustible gas or vapour rises from the 
ground, that when set on fire, it continues burning, and even affords heat for 
economical purposes. A large quantity of an impure variety of petroleum 
comes from the Birman territory in the East Indies : the country consists of 
sandy clay, resting on a series of alternate strata of sandstone and shale. 
Beneath these occurs a bed of pale blue shale loaded with petroleum, which 
lies immediately on coal. A petroleum-spring exists at Colebrook Dale, in 
Shropshire. The sea near the Cape de Verde Islands has been seen covered 
with a film of rock-oil. The finest specimens of naphtha are furnished by 
Italy, where it occurs in several places. 

In proof of the origin attributed to these substances, an experiment of 
Dr. Beichenbach may be cited, who, by distilling with water about 100 lb. of 
pit-coal, obtained nearly 2 ounces of an oily liquid exactly resembling the 
natural naphtha of Amiano, in the Duchy of Parma. 

The variations of colour and consistence in different specimens of these 
bodies certainly depends in great measure upon the presence of pitchy and 



532 PETROLEUM, NAPHTHA, ETC. 

fatty substances dissolved in the more fluid oil. Dr. Gregory found paraffin 
in petroleum from Rangoon. 

The boiling-point of rock-oil varies from about 180° to near 600° (82° -2 
to 315° -5C) ; a thermometer inserted into a retort in which the oil is under- 
going distillation, never shows for any length of time a constant tempera- 
ture. Hence it is inferred to be a mixture of several different substances. 
Neither do the different varieties of naphtha give similar results on analysis ; 
they are all, however, carbides of hydrogen. The use of these substances 
in the places where they abound is tolerably extensive ; they often serve the 
inhabitants for fuel, light, &c. To the chemist pure naphtha is valuable, as 
offering facilities for the preservation of the more oxidable metals, as potas- 
sium and sodium. 

The following are of rarer occurrence : — 

Retinite, or Betinasphalt, is a kind of fossil resin met with in brown coal; 
it has a yellow or reddish colour, is fusible and inflammable, and readily 
dissolved in great part by alcohol. The soluble portion has been called 
retinie acid by Prof. Johnston. Hatchetin is a somewhat similar substance 
met with in mineral coal at Merthyr-Tydvil, and also near Loch Fyne, in 
Scotland. Idrialin is found associated with native cinnabar, and is extracted 
from the ore by oil of turpentin, in which it dissolves. It is a white, crys- 
talline substance, scarcely volatile without decomposition, but slightly soluble 
in alcohol and ether, and composed of C 49 H 14 ; it is generally associated 
with a hydrocarbon idryl, which contains C 42 H 14 . 

Ozolzerite, or fossil wax, is found in Moldavia, in a layer of bituminous 
shale ; it is brownish and has a somewhat pearly appearance ; it is fusible 
below 212° (100°C), and soluble with difficulty in alcohol and ether, but 
easily in oil of turpentin. It appears to contain more than one definite 
principle. 



ATTEND IX. 



15 



(533) 



534 



APPENDIX. 



HYDROMETER TABLES. 



COMPARISON OF THE DEGREES OF BATJME's HYDROMETER WITH THE REAL 
SPECIFIC GRAVITIES. 



1. For liquids heavier than water. 



Degrees. 


Specific 
Gravity. 


Degrees. 


Specific 
Gravity. 


Degrees. 


Specific 
Gravity. 





1-000 


26 


1-206 


52 


1-520 


1 


1-007 


27 


1-216 


53 


1-535 


2 


1-013 


28 


1-225 


54 


1-551 


3 


1-020 


29 


1-235 


55 


1-567 


4 


1-027 


30 


1-245 


56 


1-583 


5 


1-034 


31 


1-256 


57 


1-600 


6 


1-041 


32 


1-26 T 


58 


1-617 


7 


1-048 


33 


1-277 


59 


1-634 


8 


1-056 


34 


1-288 


60 


1-652 


9 


1-063 


35 


1-299 


61 


1-670 


10 


1-070 


36 


1-310 


62 


1-689 


11 


1-078 


37 


1-321 


63 


1-708 


12 


1-085 


38 


1-333 


64 


1-727 


13 


1-094 


39 


1-345 


65 


1-747 


14 


1-101 


40 


1-357 


66 


1-767 


15 


1-109 


41 


1-369 


67 


1-788 


1G 


1-118 


42 


1-381 


68 


1-809 


17 


1-126 


43 


1 -395 


69 


1-831 


18 


1-134 


44 


1-407 


70 


1-854 


19 


1-143 


45 


1-420 


71 


1-877 


20 


1-152 


46 


1-434 


72 


1-900 


21 


1-160 


47 


1-448 


73 


1-924 


22 


1-169 


48 


1-462 


74 


1-949 


23 


1-178 


49 


1-476 


75 


1-974 


24 


1-188 


50 


1-490 


76 


2-000 


25 


1-197 


51 


1-495 







APPENDIX. 



53i 



2. Baume's Hydrometer for liquids lighter than water. 



Degrees. 


Specific 
Gravity. 


Degrees. 


Specific 
Gravity. 


Degrees. 


Specific 
Gravity. 


10 


1000 


27 


0-896 


44 


0-811 


11 


0-993 


28 


0-890 


45 


" 0-807 


12 


0-986 


29 


0-885 


46 


0-802 


13 


0-980 


30 


0-880 


47 


0-798 


14 


0-973 


31 


0-874 


48 


0-794 


15 


0-967 


32 


0-869 


49 


0-789 


16 


0-960 


33 


0-864 


50 


0-785 


17 


0-954 


34 


0-859 


51 


0-781 


18 


0-948 


35 


0-854 


52 


0-777 


19 


0-942 


36 


0-849 


53 


0-773 


20 


0-936 


37 


0-844 


54 


0-768 


21 


0-930 


38 


0-839 


55 


0-764 


22 


0-924 


39 


0-834 


56 


0-760 


23 


0-918 


40 


0-830 


57 


0-757 


24 


0-913 


41 


0-825 


58 


0-753 


25 


0-907 


42 


0-820 


59 


0-749 


26 


0-901 


43 


0-816 


60 


0-745 

1 



These two tables are on the authority of M. Francoeur ; they are taken 
from the Handworterbuch der Chemie of Liebig and Poggendorff. Baume's 
hydrometer is very commonly used on the Continent, especially for liquids 
heavier than water. For lighter liquids, the hydrometer of Cartier is often 
employed in France. Cartier's degrees differ but little from those of 
Baume. 

In the United Kingdom, Twacldell's hydrometer is a good deal used for 
dense liquids. This instrument is so graduated that the real sp. gr. can be 
deduced by an extremely simple method from the degree of the hydrometer, 
namely, by multiplying the latter by 5, and adding 1000; the sum is the 
sp. gr., water being 1000. Thus 10° Twaddell indicates a sp. gr. of 1050, 
or 1-05; 90° Twaddell, 1450, or 1-45. 

In the Customs and Excise, Sike's hydrometer is used. 



536 



APPENDIX. 



ABSTRACT 

OF DR. DALTON'S TABLE OF THE ELASTIC FORCE OF VAPOUR OF WATER AT 
DIFFERENT TEMPERATURES, EXPRESSED IN INCHES OF MERCURY. 



Temperature. 




Temperature. 




Temperature. 








Force. 






Force. 






Force. 


Fah. 


Cent. 


Fah. 


Cent. 


Fah. 


Cent. 


32° 


0°-0 


0-200 


57° 


13°-88 


0-474 


90° 


32°-2 


1-36 


33 


0°-55 


0-207 


58 


14°-4 


0-490 


95 


35° 


1-58 


34 


1°-1 


0-214 


59 


15° 


0-507 


100 


87°-77 


1-86 


35 


'l°-66 


0-221 


60 


15°-5 


0-524 


105 


40°-5 


2-18 


36 


2°-2 


0-229 


61 


16°-1 


0-542 


110 


43°-3 


2-53 


37 


2°-77 


0-237 


62 


i6°-66 


0-560 


115 


46°-l 


2-92 


38 


3°-3 


0-245 


63 


17°-2 


0-578 


120 


48°-88 


3-33 


39 


3°-88 


0-254 


64 


17°-77 


0-597 


125 


51°-66 


3-75 


40 


40.4 


0-263 


65 


18°-3 


0-616 


130 


540.4 


4-34 


41 


5° 


0-273 


66 


18°-88 


0-635 


135 


57°-2 


5-00 


42 


5°-55 


0-283 


67 


19°-4 


0-665 


140 


60° 


5-74 


43 


6°-l 


0-294 


68 


20° 


0-676 


145 


62°-77 


6-53 


44 


6°-66 


0-305 


69 


20°-55 


0-698 


150 


65°-5 


7-42 


45 


70 -2 


0-316 


70 


21°-1 


0-721 


160 


71°-1 


9-46 


46 


7°-77 


0-328 


71 


21°-66 


0-745 


170 


76°-66 


12-13 


47 


8°-3 


0-339 


72 


22°-2 


0-770 


180 


82°-2 


15-15 


48 


8°-88 


0-351 


73 


22°-77 


0-796 


190 


870.77 


1900 


49 


90.4 


0-363 


74 

75 


23°-3 


0-823 


200 


93°-3 


23-64 


50 


10° 


0-375 


23°-88 


0-851 


210 


98° -88 


28-84 


51 


10°-55 


0-388 


76 


24°-4 


0-880 


212 


100° 


30-00 


52 


11°-1 


0-401 


77 


25° 


0-910 


220 


104°-4 


34-99 


53 


ll°-66 


0-415 


78 


25°-5 


0-940 


230 


110° 


41-75 


54 


12°-2 


0-429 


79 


26°-l 


0-971 


240 


115°-5 


49-67 


55 


12°-77 


0-443 


80 


26°-66 


1-000 


250 


121°-1 


58-21 


L 56 


13°-3 


0-458 


85 


29°-44 


1-170 


300 


148°-88 


111-81 



APPENDIX. 



537 



TABLE 

OP THE PROPORTION BY "WEIGHT OP ABSOLUTE OR REAL ALCOHOL IN 100 PARI3 
OP SPIRITS OF DIFFERENT SPECIFIC GRAVITIES. (FO"WNES.) 



Sp.Gr. at 60° 
(15°-5C). 


Per cent, 
of real 
Alcohol. 


Sp. Gr. at 60° 
(15°-5C.) 


Per cent, 
of real 
Alcohol. 


Sp. Gr. at 60° 

(15°-5C). 


Per cent, 
of real 
Alcohol. 


0-9991 


0-5 


0-9511 


34 


0-8769 


68 


0-9981 


1 


0-9490 


35 


0-8745 


69 


0-9965 


2 


0-9470 


36 


0-8721 


70 


0-9947 


3 


0-9452 


37 


0-8696 


71 


0-9930 


4 


0-9434 


38 


0-8672 


72 


0-9914 


5 


0-9416 


39 


0-8649 


73 


0-9898 


6 


0-9396 


40 


0-8625 


• 74 


0-9884 


7 


0-9376 


41 


0-8603 


75 


0-9869 


8 


0-9356 


42 


0-8581 


76 


0-9855 


9 


0-9335 


43 


0-8557 


77 


0-9841 


10 


0-9314 


44 


0-8533 


78 


0-9828 


11 


0-9292 


45 


0-8508 


79 


0-9815 


12 


0-9270 


46 


0-8483 


80 


0-9802 


13 


0-9249 


47 


0-8459 


81 


0-9789 


14 


0-9228 


48 


0-8434 


82 


0-9778 


15 


0-9206 


49 


0-8408 


83 


0-9766 


16 


0-9184 


50 


0-8382 


84 


0-9753 


17 


0-9160 


51 


0-8357 


85 


0-9741 


18 


0-9135 


52 


0-8331 


86 


0-9728 


19 


0-9113 


53 


0-8305 


87 


0-9716 


20 


0-9090 


54 


0-8279 


88 


0-9704 


21 


0-9069 


55 


0-8254 


89 


0-9691 


22 


09047 


56 


0-8228 


90 


0-9678 


23 


0-9025 


57 


0-8199 


91 


0-9665 


24 


0-9001 


58 


0-8172 


92 


0-9652 


25 


0-8979 


59 


0-8145 


93 


0-9638 


26 


0-8956 


60 


0-8118 


94 


0-9623 


27 


0-8932 


61 


0-8089 


95 


0-9609 


28 


0-8908 


62 


0-8061 


96 


0-9593 


29 


0-8886 


63 


0-8031 


97 


0-9578 


30 


0-8863 


64 


0-8001 


98 


0-9560 


31 


0-8840 


65 


0-7969 


99 


0-9544 


32 


0-8816 


66 


0-7938 


100 


0-9528 


33 


0-8793 


67 




> 



538 



APPENDIX 



DR. SCHWEITZER'S 

Or THE PRINCIPAL MINERAL WATERS OP GERMANS 



Grains of Anhydrous 

Ingredients in 

One Pound Troy. 


Carlsbad. 


Ems. 


Schlesischer. 
Obersalz- 
Brunnen. 




7-2712 
0-0150 

O-Q055 

1-7775 
1-0275 
0-0048 
0-0208 
0-0012 
0-0019 

14-9019 

5-9820 

0-0184 
o'4$29 


8-0625 
0-0405 
0-0022 
0-0080 
0-8555 
0-5915 
0-0028 
0-0120 

0014 
0-4050 

0-0338 

5-7255 

0-0014 
0-3104 


7-6211 

0-0170 
1-5464 
1-5496 
0-0026 
00356 

0-3160 
2-5106 

00164 

0-8682 

0-0051 
0-2423 


Ditto of Lithia 


Ditto of Baryta 

Ditto of Strontia 






Ditto (proto) of Manganese 

Ditto (proto) of Iron 

Sub-Phos. of Lime 


Ditto of Alumina 


Sulphate of Potassa 


Ditto of Soda 


Ditto of Lithia 

Ditto of Lime 


Ditto of Strontia 




Nitr. of Magnesia 


Chlor. of Ammonium 


Ditto of Sodium 


Ditto of Lithium 


Ditto of Calcium 


Ditto of Magnesium 


Ditto of Barium 


Ditto of Strontium 


Bromide of Sodium 


Iodide of Sodium 


Fluoride of Calcium 


Alumina 


Silica 

Total - 


31-4606 
58 

Sprud. 165° 
(73°-8C) 

Neub. 138° 
(58°-8C) 

Muhl. 128° 
(53°-3C) 

Ther. 122° 
(50°C) 

Berzelius. 


16-0525 
51 

Kess. 117° 

(47°-2C) 

Krlin. 84° 

(28°-8C) 

Struye. 


14-7309 

98 

58° (14°-5C) 
Struve. 


Carbonic Acid Gas in 100 
cubic inches 

Temperature - 

Analyzed by 


} 





APPENDIX. 



539 



TABLE OF ANALYSES 

AND OF THE SARATOGA CONGRESS SPRING OF AMERICA. 



Saratoga 
Congress 
Spring. 


Kissengen. 
Ragozi. 


Marienbad. 
Kreutbr. 


Anschowitz. 

Ferclinands- 

Brunnen. 


1 

Eger. 
Franzens- 
Brunnen. 


0-8261 

0-0672 
5-8531 
4-1155 
00202 
0-0173 

0-1379 

0-1004 

00326 

1-6256 

19-6653 

0:1613 

0-0046 

00069 
0-1112 


0-0592 
4-8180 
1-3185 
00121 
0-1897 

1-2540 

5-5485 

0-0364 
39 -'3733 

3*-*6599 

0SS1 

0-1609 


5-3499 
0-0858 

0-00^8 
2-9509 
20390 
2-0288 
0-1319 

28 -'5868 
10-1727 

0-0023 

0-2908 


4-5976 
0-0507 

0-0040 
3-0085 
2-2867 
0-.0692 
0-2995 

o'-oo'io 

16 ■9022 
6*-7472 

0-5023 


3-8914 
0-0282 

0*0023 
1-3501 
" 0-5040 
00322 
0-1762 
0-0172 
0-0092 

18-3785 
6*-'9*229 

0-3548 


32-7452 
114 

50° (10°C) 
Schweitzer. 


56-7136 
96 

53° (11°-6C) 
Struve. 


51-6417 
105 

53°(11°-6C) 
Berzelius. 


34-4719 
146 

49° (9°-5C) 
Steinman. 


31-6670 
154 

54° (12°-2C) 
Berzelius. 



540 



APPENDIX. 



DR. SCHWEITZER'S 

OF THE PRINCIPAL MINERAL WATERS OF GERMANY 



Grains of Anhydrous 

Ingredients in 

One Pound Troy. 


Pyrmont. 


Spa Pouhon. 


Fachingen. 


Carbonate of Soda ■. 


4-7781 

0*0364 
0-3213 

0*0110 

0-0314 
1-6092 
0-0067 
5-0265 
00154 
2-3684 

0-8450 

0-3727 


0-5531 

0-7387 
0-8421 
00389 
0-2813 
00102 
0064 
0-0593 
00281 

0-3371 
0-37*39 


12-3328 

1*8667 
1-2983 

0-0061 

0-1267 

3-2337 

o'-0657 


Ditto of Lithia 


Ditto of Baryta 

Ditto of Strontia 




Ditto of Magnesia.. . t 

Ditto (proto) of Manganese 
Ditto (proto) of Iron 


Ditto of Alumina 


Sulphate of Potassa 

Ditto of Soda 


Ditto of Lithia 




Ditto of Strontia 


Ditto of Magnesia 

Nitr. of Magnesia 


Chlor. of Ammonium 

Ditto of Potassium ,. 

Ditto of Sodium 


Ditto of Lithium 


Ditto of Calcium 


Ditto of Magnesium 

Ditto of Barium 


Ditto of Strontium 

Bromide of Sodium 


Iodide of Sodium 


Fluoride of Calcium 


Silica 

Total 


15-4221 
160 

56°(13°-3C) 
Struve. 


3-2691 
136 

50° (10°C) 
Struve. 


18-9300 
135 

50° (10°C) 
Bischoff. 


Carbonic Acid Gas in 100 ") 
cubic inches j 


Temperature (F.) 

Analyzed bv 





APPENDIX. 



541 



TABLE OF ANALYSES 

AND OP THE SARATOGA CONGRESS SPRING OP AMERICA, Continued. 



Setters. 


Seidschiitz. 


Ptillna. 


Kreuznach. 

Elisen- 

Brunnen. 


Adelheids- 
Quelle. 

5-2443 


4-6162 
















0-0902 


0-0014 








00024 


0-0144 








0-0387 


1-4004 


5-1045 


0-5775 


0-2058 


-0-4703 


1-5000 


0-8235 


4-8045 


1-1812 


0-2980 




0-0032 




0-0072 


00012 




0-0095 




0-1495 


0-0121 


0-0007 


0-0117 


0-0026 






0-0020 


0-0088 








0-2978 


3-6705 
17-6220 

1-1287 

0-0347 

62-3535 

5-9302 


3-6000 
92-8500 

l'-9'500 

69-8145 




0-0066 


0-2685 






0-7287 


0-1845 


12-9690 


1-2225 


14-7495 


54-6917 
0-0562 
9-7358 

0-2366 
0-5494 
0-2304 
00024 


28-4608 

0-3060 
0-1500 


0-0013 






0-0086 


0-0166 


0-2265 


0-0900 


0-1320 


0-2355 


0-1922 


21-2982 


98-0133 


188-4806 


68-0190 


-35-4739 


126 


20 


7 


12 


10 


58° (14°-5C) 


58° (14°-5C) 


58° (14°-5C) 


47° (8°-3C) 


58° (H°-5C) 


Struve. 


Struve. 


Struve. 


Struve. 


Struve. 



40 



542 APPENDIX 



WEIGHTS AND MEASURES 



480-0 grains Troy = 1 oz. Troy. 

437-5 " =1 oz. Avoirdupoids. 

7000-0 " =1 lb. Avoirdupoids. 

5760-0 " =1 lb. Troy. 



The imperial gallon contains of water at 60° (15° -5C) 70,000* grains 

The pint (£ of gallon) 8,750- " 

The fluid-ounce (-5L of pint) 437-5 « 

The pint equals 34-66 cubic inches. 



The French kilogramme = 15,433-6 grains, or 2-679 lb. Troy, or 

2-205 lb. avoirdupoids. 

The grammme = 15-4336 grains. 

" decigramme = 1-5434 " 

" centigramme = 0-1543 " 

" milligramme = 0-0154 " 



The metre of France = 39-37 inches. 
" decimetre = 3-937 " 

" centimetre = 0-394 «« 

" millimetre = 0394 " 



INDEX. 



Page 

Absorption of heat 80 

Acer saccharinum 334 

Acetal 371 

Acetamide 356 

Acetate of acetetyl 215 

Acetate of oxide of amyl... 389 

Acetates 373 

Acetetyl 215 

Acetic acid 371, 395 

anhydrous 214,215 

ether 356 

Acctine 483 

Acetone 376 

Acetonitrile 373 

Acetyl 369 

Acid, acetic 371, 395 

anhydrous..? 214, 215 

aconitic 414 

acrylic 487 

aldehydic 370 

alloxanic 440 

alphaorsellic 475 

althionic 366 

amalic 450 

amygdalic 423 

anilic 406,473 

anilotic 406 

anisic 490 

anthranilic 459, 474 

antimonic 288 

arsenic 292 

arsenious 291 

aspartic 415,452 

auric 300 

azotic 123 

balenic 395 

benzilic 401 

benzoic 396 

anhydrous 215 

hetaorsellic 475 

hismuthic 275 

boracic 151 

bromic 14S 

bromo-hydrosalicylic... 405 

bromo-phenisic 528 

butyric , 393, 485 

campholic 492 

camphoric 492 

capric 394, 4S5 

caproic 394, 4^5 

caprylic 394, 485 

carbazotic 473 

carbolic... 526 

carbonic 129 

liquefaction of. fi3 

carminic 477 

cerebric 517 

cerotic 486 



Acros — continued. Page 

cerotylic 394 

cetylic 394, 4S6 

chelidonic 447 

chloracetic 318, 375 

chlorhydric 141 

chloric 145 

chlorocarbonic 131 

chlorochromic 269 

chlorohydrosalicylic 405 

chlorohyponitric 143 

chloronaphthalic 530 

chloroniceic 463 

chloronitrous 143 

chlorophenisic 528 

chlorosulphuric... 136, 364 

chlorous 144 

chlorovalerisic 393 

chlorovalerosic 393 

cholalic 510 

choleic 510 

choloidinic 511 

chrysammic 479 

chrysanilic 459, 473 

chrysolepic 479 

chrysophanic 477 

chromic 268 

cinnamic 407 

citraconic 414 

citric 413 

cocinic 484 

comenic 447 

crooonic 345 

cumaric 407 

cumic 403, 491 

cyanic ,> 426 

cyanuric 426, 427 

delphinic 485 

dextro-racemic 413 

diaiuric 442 

dithionic 135 

draconic 491 

elaidic 484 

ellagic 418 

equisetic. 414 

erythric 474 

ethalic 486 

ethionic 366 

euchronic 345 

euxanthic 479 

everuic 475 

everninic 476 

ferric 261 

formic 385,394 

formobenzoic 400 

fulminic 428 

fumaric 416 

gallic 416,418 

giyco-benzoic 402 



Acids — cont. Pa3b 

glyco-cholalic 510 

glyco-hyo-eholalic 512 

glycolic 402,501 

glucic 336 

hemipinic 446 

hippuric 402 

humic 336 

hydriodic 147 

hydrobromic 148 

hydrochloric 141 

hydrocyanic 420 

hydroferricyanic 433 

hydroferrocyanic 430 

hydrofluoric 149 

hydrofluosilicic 149 

hydroleic _487 

hydromargaric 487 

hydromargaritic 487 

hydrosalicylic 404 

hydrosulphocyanic 435 

hydrosulphuric 163 

hyocholalic 512 

hyocholic 511 

hypochloric 144 

hypochlorous 144 

hyponitric 126 

hypophosphorous ,138 

hyposulphobenzic 398 

hyposulphuric, sulphu- 
retted 135 

hyposulphurous 135 

igasuric 449 

indinic 472 

inosinic 503 

itaconic 414 

iodic 147 

iodo-sulphuric 136 

isatinic 472 

isethionic 345 

japonic 418 

kakodylic 379 

kalisaecharic 336 

kinic 447,448 

lactic 349 

lecanoric 475, 476 

levo-racemic 413 

lithic 433 

lithofellinic 512 

malamic 415 

maleic 416 

malic 414 

manganic 259 

margaric 481 

meconic 446 

melanic 404 

melasinic ,... 336 

meli.«sic 39* 

mellitic 3i5 

(548) 



544 



INDEX. 



Acids — cord. Page 

mesoxalic 440 

metacetouic 376 

metagallic 419 

metamargaric 488 

metapectic 340 

metaphosphoric ... 213 

methionic .., 366 

metoleic 487 

mueic 344 

muriatic 141 

mykomelinic 440 

myristic 484 

myronic 493 

nitric 123 

nitrasinic 490 

nitrobenzoic 397 

nitrococcusic 477 

nitrocumic 403 

nitrophenasic 528 

nitrophenesic 528 

nitrophenisic 528 

nitre-salicylic 406,473 

nitrotoluylic 403 

nitrous 126 

renanthic 257 

oenanthylic 395, 488 

oleic 482 

oleophosphoric 517 

opianic 445 

orsellinic 474, 475 

oxalic 341 

oxalovinic 359 

oxaluric 440 

oxamic 343 

oxalinic 461 

palmitic 484 

parabanic 440 

paratartaric 413 

parellic 476 

poetic 341 

pelargonic 357, 395 

pontathionic 136 

perchloric 145 

perchromic 269 

periodic 148 

permanganic 259 

phoceni~ .. 485 

phosphethylic 359 

phosphobiethylk 359 

phosphoric 138 

anhydrous 213 

bibasic 213 

glacial 213 

monobasic 213 

tribasic 212 

phosphorous 138 

phosphovinic 358 

phthalic 529 

picric 473 

pimaric 494 

pinic 493 

propionic 376, 395 

prussic 420 

ourpuric 443 

purreic. 479 

pyrogallic 419 

pyromeconic 447 

pyromucic 345 

pyrophosphoric 213 

pyrotartaric 412 

racemic 413 

retinic 532 

rhodizonic 315 



Acids — cord. Page | 

ricinoleic 488 

rubiacic 478 

rubic 418 

saccharic 343 

sacchulmic 336 

salicylic 406 

salicylous 404 

sebacic 484 

selenic 136 

selenious 136 

stearic 481 

styphnic 479 

suberic 345,484 

succinic 484 

sulphamylic 390 

sulphindigotic 471 

sulphindylic 471 

sulphobenzoic 398 

sulphoglyceric 483 

sulpholeic 487 

sulphomargaric 487 

sulphomethylic 3S3, 384 

sulphonaphthalic 529 

sulphophenic 526 

sulphosaecharic 335 

sulphotoluoiic 495 

sulphovinic 358 

sulphuric 133 

sulphuric, anhydrous... 135 

sulphurous 132 

syMc 493 

tannic 416 

tartaric 410 

tartaric, anhydrous 412 

tartralic 412 

tartrelic 412 

tartrovinic 359 

tauro-cholalic 511 

tauro-hyo-cholalic 512 

telluric 290 

tellurous 290 

tetrathionic...; 135 

thionuric 441 

toluylic 403 

trithionic....i 135 

ulmic \... 336 

441 

436, 438 

476 

390, 395 
492 
368 

/ 



monobasic 

notation of. 

oxygen- theory 

polybasic 

terminology of ,.£ e . 

tribasic J&i 212 

vegetable 410 

Aconitates 41 1 

Aconitic acid 414 

Aconitine 451 

Aconituiri, acid of 414 

Aconitum napellus 451 

Acrolein 482, 4S7 

Acrylic acid 487 

Affinity, chemical 183 

After-damp of coal-mines 123 




jt»AGB 

Air-pum? 34, 35 

Air, atmospheric 120 

Alanine 350, 370, 467 

Albite 250 

Albumin 495 

Albuminous principles.... 496 

Alcohol 346 

absolute 346 

butyl- 392, 395 

capryl- 395, 488 

cerotyl- 395,486 

cetyl- 395, 486 

ethal- 486 

Alcohols, generally 393 

Alcohol, melissic 394,480 

table of, in aqueous mix- 
tures 537 

Aldehyde 351, 379 

bases from 467 

resin' 370 

Aldehydic acid 370 

Alembroth, sal 305 

Algaroth, powder of. 289 

Alizarin 477 

Alkalimeter 227 

Alkalimetry 226 

Alkaloids 444 

artificial 453 

Alkargen 379 

Alkarsin 377 

Allan toin....'. 438 

Alliaria offiiinalis, oil of.. 493 

Alloxan 439 

Alloxanic acid 440 

Alloxantin 441, 451 

Alloys 199 

of copper 278 

Allyl 493 

oxide of. 493 

sulphide of 493 

sulphocyanide of. 493 

Almonds, oil of bitter 396 

Aloes 479 

Alphaorsellic acid 475 

Althionic acid 366 

Alums 249 

Alum, common 249 

Roman 249 

Alumina 248 

acetate of. 373 

analytical remarks on.. 25C 

silicates of 249 

sulphate of. 249 

Aluminium 248 

chloride of. 248 

Alum stone 249 

Amalgam, ammoniacal... 232 

Amalgam 199,306 

Amalic acid 450 

Amarine 401, 466 

Amber 4S4, 494 

Amidin 338 

Amidogen 235 

Amidogen-bases 454 

Ammelide 436 

Ammeline 436 

Ammonia 162 

acetate of 373 

alum 249 

analytical remarks on.. 235 

benzoate of 397 

cyanate of 427 

malate of. 415 



INDEX. 



545 



Ammonia — cont. Page 

oxalate of 343 

purpurate of 442 

tartrate of 411 

urate of 438 

Ammonium 201,232 

cyanide of. 425 

ferrocyanide of 433 

salicylideof 404 

Amnii liquor 508 

Amorphous quinine 448 

Amygdalic acid 423 

Amygdalin 396, 423 

Amylaceous group 333 

Aniyl and its compounds 388 

series, bases of the 458 

Amylamine 458 

-urea 458 

Amyl-ammonia 458 

Amylene 390 

Amylic ether 389 

mercaptan 390 

Amylotriethyl - ammo- 
nium, oxide of 464 

Analcime 250 

Analysis, ultimate, of or- 
ganic bodies 320 

Analysis of carbonates.... 228 
Analytical method of che- 
mical research 115 

Anhydrous acids 214 

Anilic acid 406. 473 

Aniline .... 399, 459J 463 

homologues of 462 

-urea 462 

Auilotic acid 406 

Animal heat 507 

body, components of.... 496 

Aniseed, oil of 490 

Anisic acid 490 

Auisoin 490 

Auisol 491 

Anisyl, hydride of. 490 

Anthranilic acid 459, 474 

Antiarin 452 

Antimonic acid 288 

Antimony 287 

bases 469 

crude 289 

potassa, tartrate of 411 

Aqua regia 143 

Arabin 340 

Archil 474 

Argandlamp 159 

Argol 347, 410 

Aricine 448 

Aridium 266 

Arragonite 242 

Arrow poison of central 

America 451 

Arrowroot 339 

Arsenic acid 292 

Arsenic and its com- 
pounds 291 

analytical details 293 

detection in organic 

mixtures 293 

Arsenious acid 291 

Artemisia 452 

Arterial blood 503 

Assafoetida 479 

oil of 493 

Aspnragin 415, 452 

Asparagus 452 

40* 



Page 

Aspartic acid 415, 452 

Aspen 452 

Asphaltene 531 

Asphaltum 531 

Astatic needle 101 

Atmosphere, chemical re- 
lations of 120 

composition and anar 

lysis of 121 

physical constitution of 34 

purifying 244 

vapour of water in 61 

Atmospheric electricity... 97 

Atomic theory 182 

Atomic weight 183 

Atoms 182 

Atropa belladonna 451 

Atropine 451 

Attenuation of wort 348 

Attraction 1S3 

Augite 247 

Auric acid 300 

Auschowitz, water of. 539 

Axes of crystals 206 

Axinite 250 

Azobenzol 399 

Azotic acid 123 

B. 

Badian-oil 491 

Balenic acid 395 

Balsams 493 

Balsam, Canada 494 

copaiba 494 

Peru 40S, 495 

Tolu 403,408, 495 

Barilla 225 

Barium 237 

ferrocyanide of 432 

salicj T lide of 404 

Barley sugar 334 

Barometer 38 

Baryta and its hydrate 

237, 238 

acetate of 373 

analytical remarks on.. 238 

aconitate of. 414 

fulminate of 429 

tartrate of. 411 

Bases 109 

from aldehyde 467 

amidogen- 454 

from animal oil 465 

antimony- 469 

organic, containing 

chlorine 460 

from coal-tar-oil 465 

of the ethyl-series 455 

imidogen- 454 

artificial, containing 

mercury 306 

mixed artificial 463 

nitrile- 454 

from volatile oils by 

ammonia 465 

organic 444 

organic, artificial 453 

phosphorus- 468 

containing platinum.... 309 

Bassorin 340 

Battery, constant 193 

Baume's h3 r drometer 535 

Bay salt 232 



Page 

Beeberine 451 

Beer 347 

Beetroot, sugar from 334 

Bell metal 279 

Bengal light 290 

Benzamide 400 

Benzile 401 

Benzilic acid 401 

Benzimide 401 

Benzine 398 

Benzoates 397 

Benzoate of benzoyl 215 

of phenyl 527 

Benzoic acid 396, 452 

anhydrous 215 

Benzoicine 483 

Benzoin 480 

Benzol 398 

Benzol, homologues of.... 462 

Benzoline 466 

Benzone 398 

Benzonitrile 401 

Benzophenone 398 

Benzoyl 401 

and its compounds 396 

benzoate of 218 

Berberine 451 

Berberis vulgaris 451 

Bergamot, oil of 490 

Berthollet's fulminating 

silver 299 

Bervl 251 

Berylla 251 

Beryllium 250 

Betaorcin 476 

Betaorsellic acid 475 

Bezoar stones 512 

Biamylanime 458 

Biamyl-ammonia 45S 

Bibasic acids 212 

Biborate of soda 231 

Bicarbonate of potassa.... 221 

Bicarbonate of soda 226 

Bichloraniline 460 

Bichlorethylamine 456 

Bichloride of tin 283 

Bichlorisatin 473 

Bichlorokinone 449 

Bichlorosaligenin 406 

Bichromate of potassa 2C9 

Biethylamine 456 

-urea 456 

Biethyl-ammonia 456 

Biethyl-amylamine 464 

Biethylaniline 463 

Biethyl-pheuylamine 463 

Biethyl-phenyl-ammo- 

nium, oxide of 463 

Biethylo-toluidine 463 

Biliary calculi 4S7 

Bile 509 

test of Pettenkofer 511 

Bilin 511 

Bimethylamine 458 

Binary theory of salts 213 

Binitrobenzoi 399, 460 

Binitrotoluol ,495 

Binoxide of barium 237 

of protein 500 

of tin 282 

Biscuit 254 

Bismuth 274 

inalytical remarks 276 



546 



INDEX. 



Page 

Bismuthic acid 275 

Bisulpliate of potassa 221 

of soda 229 

Bisulphide of carbon 1G9 

Bitter almonds, oil of 396 

Bitumen 530 

compact 531 

elastic 531 

Black flux 294 

Bleaching 24-4 

Bleaching powder 243 

testing its value 244 

salts 144 

Blende 273 

Blood 503 

arterial 503 

circulation of the 503 

corpuscles 504 

discs 504 

globules 504 

serum of 504 

venous 503 

Blowpipe 158 

Blue ink 432 

light 290 

Prussian 432 

Turnbull's 433 

Boilers, deposits in 242 

Boiling point 54 

Bones 518 

Boracic acid 151 

ether 355 

Borax 231 

Borneene 492 

Borneol 492 

Boron 151 

chloride of. 109 

fluoride of 151 

Brass 278 

Brazilwood 478 

Bread 349 

Brewing 348 

British gum 339 

Bromal 307 

Bromaniline 460 

Bromanisal 491 

Bromic acid 148 

Bromide of amyl e>89 

of arsenic 292 

of benzoyl 400 

of cyanogen 430 

of ethyl 353 

of potassium 224 

Bromine 148 

Bromisatin 472 

Bromoform 367, 3S7 

Bromo-hydrosalicylic acid 405 

Bromophenisic acid 528 

Bromosamide 405 

Brown coal 530 

Brucine 444 

Bunsen's battery 194 

Butter 485, 508 

of antimony 288 

Butyl 392 

Butylen6 392, 398 

Butylic alcohol 392, 395 

Butyric acid 395, 485 

ether 357 

Butyrhi 485 

C. 
Cacao butter 484 

Cadet's fuming liquid 377 



Page 

Cadmium 274 

analytical remarks 274 

Caffeine 450 

murexide 451 

Calamine 273 

Calcium and its com- 
pounds 239 

fluoride of 243 

analytical remarks 244 

Calc sinter 242 

Calculi, biliary 487 

urinary 443, 515 

fusible 516 

mulberry 516 

Calomel 303 

Camphene 489 

Caniphogen 492 

Campholene 492 

Campholic acid 492 

Camphor 492 

artificial 489 

Camphoric acid 492 

Camphylene 4S9 

Canada balsam 494 

Cane-sugar.., 333 

Candle, flame of. 158 

Candles, stearin 488 

Canthcxddin 487 

Caoutchouc 494 

mineral 531 

tubes (note) 129 

Caoutchoucin 494 

Capric acid 395 

Capivi, oil of 490 

Capi-oic acid 395,485 

Caprovl 395, 488 

Caprylicacid 395, 488 

alcohol 396,488 

Caramel 334 

Carbamide 437 

Carbazotic acid 473 

Carbides of hydrogen 153 

Carbolic acid 526 

Carbon 127 

chloride of 305 

bisulphide of 169 

compounds with oxy- 
gen 12S 

estimation in organic 

bodies 321 

Carbonate of baryta 238 

of copper 278 

of lead 280 

of lime 241 

of magnesia 246 

of oxide of amyl 378 

of potassa 219 

of silver 298 

of soda 225 

of zinc 273 

Carbonates 130 

analysis of 228 

of ammonia 233 

Carbonetted hydrogen, 

light 153 

Carbonic acid 129 

ether 355 

oxide 130 

Carbyl, sulphate of. 365 

Carlsbad, water of 538 

Carmine 477 

Carminic acid 47 7 

Carticr's hydrometer 535 

Carthamirj 478 



Page 

Carragheen moss 339 

Casein 498 

Cassava 339 

Cassius, purple.. 283 

Castor-oil 488 

Catechu 416, 417 

Cedar-wood, oil of 491 

Cedrene 491 

Cedriret 524 

Cellulose 341 

Cement 240 

Cements, lime 240 

Cement, Parker's or Ro- 
man 240 

Cerasin 340 

Cerebric acid 517 

Cerebrolein 517 

Cerin 486 

Cerite 251 

Cerium 251 

Cerotate of oxide of cero- 

tyl 4S6 

Cerotic acid 4S6 

Cerotyl 486 

Cerotylic acid 394 

alcohol 394, 486 

Cetyl-series 487 

Cetylic acid 394, 486 

alcohol 394, 4S 6 

Chalk . 241 

stones 438 

Chameleon, mineral 259 

Charcoal, animal and ve- 
getable 123 

Chelidonic acid 447 

Chelidonium majus 447 

Chemical philosophy 170 

Chimneys, action of. 57 

Chinese wax 4S6 

Chinoline 464 

Chinoidine 44S 

Chloracetates 375 

Chloracetic acid 318, 375 

Chloral 366, 370 

insoluble 366 

Chloranile 449 

Chloraniline 460 

Chlorate of potassa 221 

Chloretheral 367 

Chlorhydric acid 141 

Chloric acid 145 

Chloride of aluminium... 24S 

of ammonium 233 

of amyl 389 

of antimony 288 

of arsenic 292 

of barium 237 

of benzoyl 399 

of boron 169 

of calcium 240 

of chromium 268 

of cinnamyl 408 

of copper 278 

of cyanogen 430 

of ethyl! 353 

Of gold 300 

of hydrocarbon 156 

of iodine 168 

of kakodyl 378 

of lime 243 

of magnesium 245 

of methyl 382 

of mercury 304 

Of nitn-geu 167 



INDEX 



547 



Chloride — cord. Page 

of olefiantgas 363 

of phenyl 527 

of phosphorus 168 

of platinum 308 

of potassium 223 

of silicium 169 

of silver 298 

of sodium 231 

of sulphur 168 

of zinc 273 

Chlorides of carbon.. 365, 366 

Chlorine 139 

compounds with . 143 

estimation of, in organic 

bodies 32S 

peroxide of. 144 

Chlorisatin 472 

Chlorobenzol 399 

Chlorobenzide 399 

Chloro-carbonic acid 131 

ether 357 

Chlorochromic acid 269 

Chlorocinnose 408 

Chloroform 366, 386 

Chloro-hydro-salicylicacid 405 

Chloro-hypouitric acid 143 

Chlorokinone 449 

Chlorometry 244 

Chloroniceic acid 463 

Chloronicene 463 

Chloronicine 463 

Chloro-nitrous acid 143 

Chloro-phenisic acid 527 

Chloro-phenusic acid 528 

Chloro-naphthalic acid 530 

Chloropicrin 473, 479 

Chloro-saligenin 406 

Chlorosamide 405 

Chloro-sulph uric acid 136, 364 

Chlorous acid 144 

Ohlorovalerisic acid 393 

Chlorovalerosic acid 393 

Cholesterin 487 

Cholestrophane 450 

Cholic acid 510 

Choloidinic acid 511 

Chondrin 500 

Cbromate of lead 267 

of potassa „ 268 

Chrome-yellow 269 

Chromic acid 268 

Chromium 267 

analytical remarks 268 

Chrysammic acid 479 

Cbrysanilic acid 459 

Chrysen 525 

Chrysolepic acid 479 

Chrysoiite . ... 247 

Chrvsophanic acid 476 

Chyle 507 

Cinchonine 447 

Cinchoratine 4-18 

Cinnabar 301, 306 

Cianamein 408 

Cinnamic acid 407 

Cinnamol 408, 495 

Cinnamon, oil of 407 

Cinnamyl and its com- 
pounds 407 

Circular polarization of 

light 76 

Circulation of the blood.. 503 
Citraconic acid 411 



Page 

Citrates 414 

Citric acid 413 

Clarifying wines and beer 502 

Clay iron-stone 263 

origin of 249 

Cleavage 203 

Coal, brown 530 

gas 155 

Cobalt 271 

analytical remarks on.. 272 

cyanide of 426 

acetate of 374 

Cobalto-cyanogen 433 

Cobalt-ultramarine .. 272 

Cocculus indicus 452 

Coccus cacti 477 

Cochineal 477 

Cocinic acid 484 

Cocoa-oil 484 

Codeine 446 

Cohesion 184 

Coke 128 

Colchicine 450 

Collodion 344 

Colophene 490 

Colophony 493 

Colouring principles, org. 470 

Columbium 286 

Combination by volume.. 177 

by weight 172 

Combining quantities 174, 176 

Combustion 156 

Comenic acid 447 

Common salt 231 

Compass, mariner's 89 

Combination, laws of. 172 

Concretions, gouty 438 

Condensation of gases and 

vapours 61,62 

Conduction of heat, 52 

Conicine 450 

Conine 450 

Constant battery 193 

Cotarnine 446 

Copaiba balsam 494 

Copal 494 

Copper 277 

acetates of 375 

alloys of. 278 

analytical remarks on.. 278 

ferroc3 r auide of 433 

salicylide of 404 

Cork 484 

Corn-oil 393 

Corundum 248 

Corrosive sublimate 304 

Cream of tartar 411 

Croconic acid 345 

Crown-glass 252 

Crucibles 255 

Cryophorus 65 

Crystals 202 

Crystallization 202 

Crystalline forms 202 

Crystallization, water of.. 202 

phenomena of 202 

Cube 206 

Cubebs, oil of 490 

Cudbear 474 

Cumaric acid 407 

Cumarin 406 

Oumic acid 403. 491 

Cumidine 4o2| 



Page 

Cumin oil 491 

Cuminol 403. 491 

Cumol 403, 462,' 492 

Curarine 451 

Curd 499 

Cyanates 427 

Cyanethine. 354 

Cyamelide 426 

Cyanic acid 426 

Cyanide of amyl 389 

of benzol 400 

of ethyl 354 

of hydrogen 420 

of kakodyl 379 

of methyl 383 

of phenyl 527 

Cyanides <- 424 

Cyaniline 460 

Cyanite 250 

Cyanogen 420 

bromide of. 430 

chloride of. 430 

compounds and deriva- 
tives 420 

iodide of. 430 

Cyanuric acid 426, 427 

Cymol 403, 491 

Cystic oxide 443, 51G 

D. 

Dammar resin 494 

Daniell's battery 193 

Dutch liquid 155, 318, 363 

Datura stramonium 451 

Daturine 451 

Daphne mezereum 452 

Daphnin 452 

Decay 320 

Declination, magnetic 88 

Decolorization by charcoal 128 

Deliquescence 202 

Delphinic acid 485 

Delphinine 451 

Delphinium staphisagria 451 
Dew, origin and cause of 81 

Density 27 

Density of vapours, deter- 
mination of 330 

Dextrin 338 

Dextro-racemic acid 413 

Diabetes 335, 514 

insipidus, sugar from... 336 

Dialm-ic acid 442 

Diamagnetic bodies 89 

Diamond 127 

Diastase 839 

Diathermancy 82 

Didymium 251 

Diffusion 112 

false 507 

Digestion 521 

Dimorphism 203 

DippeFs oil 465 

Disacryle 487 

Disinfection 141, 244 

Disinfecting solution of 

Labarraque 24.* 

Disposing influence 186 

Distillation 58 

dry or destructive 319 

Dithionic acid 1-.5 

i ode' ahedron 206 

Double salts 202 



518 



INDEX. 



Page 

Draconic acid 491 

Dragons' blood 494 

Dropsy, fluid of. 508 

Dyes, red and yellow 477 

Dyeing, action of 470 

Dyslysin 511 

E. 

Earthenware 254,255 

Eblanin 388 

Ebullition 54 

Effervescing draughts 411 

Efflorescence 202 

Eger, water of. 539 

Egg, white of 496 

Elaidic acid 484 

Elaidin 484 

Elain 480 

Elais guianensis 483 

Elaldehyde 370 

Elaterin 452 

Electric eel 99 

Electric machine 94 

Electrical current 97 

Electricity 92 

Electro-chemical decompo- 
sition 187 

Electrodes 187 

Electrolysis 187 

Electro-magnetism 100 

Electrophorus 97 

Electro-plating 195 

Electrolytes 187 

Electrotype 194 

Elementary bodies 103 

substances, table of 176 

substances, table of sym- 
bols 180 

Elements 104 

Elemi, oil of. 490 

Ellagic acid 418 

Emerald 251 

Emery.. 248 

Emetine 451 

Ems, water of 538 

Emulsin 422 

Epsom salt 246 

Equator, magnetic ... 89 

Equisetic acid.. 413 

Equisetum, acid of 414 

Equivalents, table of 176 

volume 178 

law of. 174 

Erbium 251 

Eramacausis 320 

Erytrarsin 379 

Erythric acid 474 

Erythroprotide 500 

Essence of turpentin 489 

Essential oils 488 

Ethalic acid 486 

alcohol 486 

Ether 351 

acetic 356 

acetic, chlorinetted 367 

boracic 355 

butyric 357 

carbonic 355 

chlorocarbonic 357 

cyanic 428 

rvanuric 428 

formation of 360 

formic 356 

fr.-rmic. chlorinetted 36" 



Ether — cont. Page 

hydriodic 353 

hydrobromic 353 

light hydrochloric 353 

margaric 357 

muriatic, heavy 367 

nitric 354 

nitrous .. 355 

oenanthic 357 

oxalic 356 

oxamic 356 

phosphoric 354, 359 

preparation of. 360 

silicic 355 

sulphuric 354 

sulphurous 354 

valerianic 357 

Etherin 362 

Etherole 362 

Ethers, compound 352 

of fatty acids 357 

Ethionic acid 366 

Ethyl 352 

bromide of. 353 

chloride of. 353 

cyanide of. 354 

iodide of. 353 

oxide of 351 

oxide of, compounds of, 
with acids, see Ether. 351 

oxide of, cyanate of 428 

oxide of, cyan urate of... 428 

-series, bases of 455 

sulphide of. 354 

-theory 352 

-zinc 368 

Ethylamine 455 

-urea 456 

Ethylamyl aniline 464 

Ethyl-ammonia 455 

Ethylaniline 463 

Ethylene 362 

Ethylophenvlamine 464 

Ethylo-toluidine 464 

Ethyl-oxamide 455 

Euchlorine 145 

Euchrone 345 

Euchronic acid 345 

Eudiometer 116, 122 

Euclase 250 

Eupion 523 

Euxanthic acid 479 

Euxanthone 479 

Evaporation 59 

Evernic acid 475 

Everniuic acid 476 

Evernia prunastri 475 

Expansion by heat 41 

of fluids 46 

of gases 48 

of solids 44 

F. 

Fachingen, water of 540 

Fats 480 

Fatty acids 395 

Fecula 337 

Felspar 249 

Fennel-oil 491 

Fermentation 345 

butyric 349 

lactic 349 

vinous 346 

viscous 351 

Ferments.... 345 



Page 
Ferricyanide of hydrogen 433 

Ferricyanides 433 

Ferricyanogen 433 

Ferridcyanogen 433 

Ferrocyanides 426, 431, 433 

Ferrocyanogen 430 

Fibrin 497 

Fire, blue 290 

damp 153 

red and green 239 

Flame, structure of. 156 

Flint-glass 252 

Florence flasks 125 

Fluids, expansion of 46 

Fluoride of boron 152 

of calcium 243 

of siliciuni 150 

Fluorine 149 

Fluor-spar 243 

Food 518 

Formates 386 

Formicacid 385,395 

ether 356 

Formo-benzoic acid 400 

Formo-methylal 387 

Formulas 329 

empirical 329 

rational — 329 

French weights and mea- 
sures 542 

Frigorific mixtures 53 

Fruit-sugar 335 

Fucusamide 466 

Fucusine 466 

Fucusol 466 

Fulminates 428 

Fulminating silver of Ber- 

thollet 299 

Fulminic acid 428 

Fumaramide 416 

Fumaric acid 416 

Furfurine 465 

Furfurolamide 466 

Furfurol 465 

Furnace, reverberatory... 157 

Fusel-oil 3S8 

of grain-spirit 393 

Fusible metal 275 

Fustic wood 479 

G. 

Gadolinite 251 

Galena 279 

Gallates 418 

Gallic acid 416, 418 

Galls, nut 417 

Galvanism 97 

Galvanometer 83 

Galvanoscope 83,101 

Garancin 47S 

Garlic, oil of. 493 

Garnets 251 

Gas, coal and oil 355 

oleflant 154 

Gases, diffusion of. 112 

expansion of. 48 

management of 106, 111 

122, 129, 132 
physical constitution of 34 

specific heat of. 67 

Gas-holder 107 

Gastric juice 521 

Gaultheria procumbens, 
oil of 406 



INDEX. 



549 



Page 

Gelatin 500 

-sugar 501 

Gentianin 451 

German silver 271 

Geyser springs of Iceland 119 

Gilding 301 

Glass, coloured 253 

manufacture of. 252 

variety of 252 

soluble 254 

Glauber's salt 229 

Gliadin 519 

Globulin 504 

Gluric acid 336 

Glucinum 252 

Glucose 334 

Glue 502 

Gluten 337, 519 

Glutin 337 

Glycerin 481,483 

Glyco-benzoic acid 402 

Glycocine 402, 501 

Glycocoll 501 

Glyco-cbolalic acid 510 

Glyco-byocbolalic acid 512 

Glvcolaniide 402 

Glycolic acid 402, 501 

Glycyrrbizin 336 

Goniometry 204 

Gold, analytical remarks. 300 

and its compounds 299 

cvanide of 426 

-dust 299 

-leaf 300 

standard of England.... 299 

Goulard water 374 

Gouty concretions 43S 

Gramme 542 

Grape sugar 334 

Grapbite 128 

Grass oil 490 

Gravity, specific 27 

Greenbeart timber 451 

Green fire 239 

Green salt of Magnus 309 

Groups, isornorphous 211 

Grove's battery 194 

Guanine 443 

Guano 443 

Gum 340 

arabic 340 

benzoin 495 

British 339 

of cherry-tree 340 

tragacanth 340 

Gun cotton 344 

Gun metal 279 

Gunpowder 220 

Gutta percba 494 

Gypsum 241 

H. 
Hahnemann's soluble 

mercury 303 

Halitus 504 

Haloid salts 201 

Hardness of water 241 

permanent 241 

temporary 242 

Harmaline 450 

Harmine 450 

Haxcbetin 532 

Heat, absorption 80 



Heat — cont. Page 

animal 507 

capacity for specific 66 

conduction of 52 

latent 53 

pbenomena of. 41 

radiation 79 

reflection 79 

transmission 82 

Heavy spar 238 

Helicin 406 

Helicoidin 406 

Hemihedral crystals 209 

Hemipinic acid 446 

Hematite 261 

Hematosin 504 

Hematoxylin...! 479 

Hepar sulphuris 222 

Herrings, liquor of salt.... 458 

Hesperidin 452 

Heulandite 251 

Hippuric acid 402 

Homologous, term 396 

Homologues of aniline.... 462 

of benzol 462 

of tbe glycocine-series... 501 

of tbe salicyl-series 491 

Honeystone 345 

Hop 348 

oil of. 490 

Horneblende 247 

Horn silver 298 

Horse-radish, oil of 493 

Huano 443 

Humic acid 

Humus 336 

Hydrate of oil of turpen- 

tin 

Hydrates, term 118 

Hydride of anisyl 490 

Hydride of benzoyl 396 

Hydride of cinnamyl 407 

Hydriodic acid 147 

ether 353 

Hydrobenzamide 400 

Hydrobromic acid 148 

ether 353 

Hydrocarbon, chloride of 155 

Hydrochloric acid 141 

ether, heavy 367 

Hydrocyanic acid 420 

Hydroferricyanic acid 433 

Hydroferrocyanic acid 430 

Hydrofluoric acid 149 

Ilydrofluosilicic acid 150 

Hj^drogcn 110 

antimonetted 

arsenetted 292 

binoxide of. 115, 119 

carbides of 153 

carbonetted 153 

estimation in organic 

bodies 321 

persulpbide 165 

phosphoretted 166 

selenietted 165 

sulphuretted 161 

Hj T drokinone, colourless.. 448 

green 44S 

Hydroleic acid 487 

Hydromargaric acid 487 

Hydromargaritic acid 487 

Hydrometer tables 534 

Hydrosalicylic acid 404 



Page 
Hydrosulphocyanic acid.. 435 

Hydrosulphuric acid 1G3 

Hygrometer, dew-point... 66 

wet-bulb 62 

Hyocholalic acid 512 

Hyocholic acid 511 

Hyoscyamine 451 

Hyoscyamus niger 457 

Hyodyslysin 512 

Hypochloric acid 144 

Hypochlorous acid 144 

Hyponitric acid 126 

Hypophosphorous acid.... 138 
Hyposulphate of silver... 298 

Hyposulpbate of soda 229 

Hyposulphite of silver.... 298 

Hyposulphites 135 

Hyposulphobenzic acid... 398 

Hyposulphuric acid 135 

bisulphuretted 135 

sulphuretted 135 

trisulphuretted 136 

Hyposulphurous acid 135 

I. 

Iceland moss 239 

Idrialin 532 

Imidogen-bases 454 

Inclination, magnetic 88 

Incrustations in boilers.. 242 

Indian yellow 479 

Indigo 470 

red 470 

vat 240 

white, or de-oxidized.... 471 

Indin 472 

Indinic acid 472 

Inosinic acid 503 

Inosite 503 

Ink, label 494 

blue, sympathetic 271 

Inulin 239 

Iodic acid 147 

Iodide of amyl 388 

of arsenic 292 

of benzoyl 400 

of cyanogen 430 

of ethyl 353 

of kakodyl 379 

of mercury 305 

of methyl 383 

of nitrogen 167 

of silver 299 

Iodine 146 

chloride of. 168 

Iodoform 387 

Iodo-sulphuric acid 136 

Ipecacuanha 451 

Iridium 312 

Iron, acetate of. 374 

analytical remarks on.. 263 

and its compounds 259 

cyanide of 426 

manufacture of 263 

protoxide, lactate of..... 351 
sesquioxide, benzoate of 397 

Isatin 471 

Isatinic acid 472 

Isatyde 472 

Isetbionic acid 366 

Isinglass 500 

Isomeric bodies 318 

Isomorphism...... 209 



550 



INDEX. 



Page 

Isomorphous 209 

Itacouic acid 414 

J. 

Jade 247 

Japonic acid 418 

Jet 530 

Jew's pitch 531 

Juice, gastric 521 

Juniper, oil of 490 

K. 

Kakodyl 377 

-compounds 377 

Kakodylic acid 379 

Kalisaccharic acid 336 

Kaolin 255 

Kapnomor 524 

Katalysis 186, 345 

Kelp 146 

Kermes mineral 2S9 

Kinic acid 447,448 

Kino 416 

Kinone 448 

Kish 128 

Kissingen, Ragozi water.. 539 

Kreatin 502 

Kreatinine 450, 502 

Kreosote 524 

Kreuznach 541 

Kyanol 465 

Kyan's method of preserv- 
ing timber. 305 

L. 

Labarraque's disinfecting 

fluid 243 

Label ink 494 

Lac 494 

Lactamide 35o 

Lactates 350 

Lactic acid 349 

Lactide 350 

Lactin 336 

Lactone 350 

Lake 470 

Lamp, argand 159 

flame of. 159 

safety 161 

spirit 159 

witbout flame 371 

Lampblack 128 

Land and sea breezes, 

cause 81 

Lanthanium 251 

Laughing-gas 125 

Laumonite 250 

Laurel oil 490 

Lavender, oil of. 492 

Lead 279 

acetates of 374 

niloysof. 281 

analytical remarks on... 281 

benzoate of 397 

binoxide of. 279 

malate of. 415 

-plaster 483 

protoxide of 279 

red 279 

sugar of. 374 

•tree 195 

white 2S0 

Leaven 349 

Le^auoraparella 476 



Lecanora — cord. Page 

tartarea 476 

Lecanoric acid 474, 475 

Lcgumin 520 

Lemons 413 

oil of 490 

Leucine 500 

Leucoline 464 

Leukol 465 

Levo-racemic acid 413 

Leydenjar 96 

Lichens 474 

Light.. 71 

blue or Bengal 290 

chemical rays of 77 

polarized 75 

Lightning rods 97 

Lignin 341 

Lignite 530 

Lignone 388 

Lime 239 

acetate of 373 

aconitate of. 414 

analytical remarks 244 

benzoate of. 397 

carbonate of. 241 

chloride of. 243 

lactate of 351 

malate of 415 

oxalate of. 343 

phosphates of. 242 

tartrate of. 411 

Limestone 241 

Liquefaction of gases 62 

Liquor ammonias 162 

amnii 508 

Liquorice sugar 336 

Litharge 279 

Lithia.. 235 

Lithicacicl 438 

Lithium 235 

Lithofellinic acid 512 

Litmus 474 

Loadstone 8, 261 

Loaf-sugar 334 

Logwood 478 

Lupulin 348 

Lungs 506 

Lymph 507 

M. 

Madder 477 

Magnesia 245 

acetate of. 373 

aconitate of 414 

alba 246 

analytical remarks on.. 247 

carbonate of 246 

phosphate of. 246 

silicates of 247 

sulphate of. 246 

tartrate of. ■. 411 

Magnesium 245 

chloride of. 245 

Magnetism 86 

Magnus, green salt of. 309 

Malachite 278 

Malamic acid 415 

Malamide 415 

Malates 415 

Maleic acid 416 

Malic acid 414 

Malleability of metals 19S 

Malting 348 



Tage 

Manganese, acetate of. 374 

and its compounds 256 

assay of. 257 

Manna sugar 337 

Mannite 337 

Manures 522 

Maple, sugar from 334 

Marble 241 

artificial coloured 241 

Marc-brandy, fusel-oil of.. 393 

Margaric acid 481 

ether 357 

Margarin 480, 481 

Margarone 482 

Marienbad, water of 539 

Mariotte's law 38 

Marsh gas 153 

Marsh mallow 452 

Marls 250 

Massicot 279 

Mastic 494 

Meadow-sweet, oil of. 404 

Measures 542 

Meat 518 

Meconic acid 446 

Meconine 446 

Meerschaum 247 

Melam 436 

Melamine 436 

Melauiline ' 4^1 

Melanic acid 404 

Melasinic acid 336 

Melissic acid 394 

alcohol 394,486 

Mellite 345 

Mellitic acid 345 

Mellon 435 

Membranous tissues 516 

Membranes, mucous 508 

Mercaptan. 367 

methyl- 387 

Mercury 301 

acetates of. 375 

analytical remarks on... 306 

cyanide of 425 

fulminate of. 429 

its compounds 302 

Meridian, magnetic S8 

Mesitilol 376 

Mesityl 376 

Mesotype 250 

Mesoxalic acid 440 

Metacetone 376 

Metacetonic acid 376 

Metaldehyde 370 

Metagallic acid 419 

Metals 197 

classification 216 

Metamargaric acid 487 

Metapectin 340 

Metapectic acid 340 

Metaphosphoric acid 213 

Metastyrol 405 

Meteorites 259 

Methionic acid 366 

Methyl 3S1 

Methylamine 457 

-urea 4$7 

Methyl-ammonia 457 

Methyl-compounds... 381. 382 

Methyl-ether 3«2 

Methyl-ethyl-amylamine. 464 
-urea 457 



INDEX. 



551 



Page 
Methyl - ethyl - amylophe- 
nylammonium, oxide 

of 464 

Methyl-mercaptan 3S7 

Methylo-biethyl-amyl-am- 

monium, oxide of 464 

Methyl-salicylate of, oxide 

of 491 

Methyl-series, bases of the 457 

Metoleic acid 487 

Metre 542 

Mica 250 

Microcosmiu salt 230 

Milk 508 

spirit from 509 

Milk-sugar 336 

Mindererus, spirit of. 373 

Mineral chameleon 259 

waters, table of. 538 

Molasses 334 

Molecular actions 184 

Molybdenum 284 

Momordica elaterium 452 

Monobasic acids 212 

Mordant 283 

Mordants 470 

Morphia 444 

Morphine 444 

Mortar 240 

Mosaic gold 283 

Mucic acid 344 

Mucilage 340 

Mucous membranes 508 

Mucus 508 

Mulberry calculus 516 

Multiple proportions 173 

Multiplier 83 

Murexan 443 

Murexide 442 

caffein 450 

Muriatic acid 141 

ether, heavy 367 

Muscovado sugar 334 

Mushroom sugar 337 

Must 347 

Mustard, oil of. 492 

bases from the oil of.... 466 

Mykomelinic acid 440 

Myricin 492 

Myristicacid 484 

Myristica moschata 484 

Myronic acid 493 

N. 

Naphtha 531 

Naphthalidine 462 

Naphthalan 462, 529 

Narceine 446 

Narcogenine 446 

Narcoline 445 

Nepheline 250 

Nervous substance 51 

Neutrality of salts 200 

Neutralization 176 

Nickel 269 

acetate of. 374 

analytical remarks 271 

Nicotine 450, 469 

Niobium 286 

Nitraniline 460 

Nitranisic acid 490 

Nitraniside 490 

Nitrate of ammonia 234 



Nitrate — cord. Page 

of baryta 238 

of bismuth 275 

of lead ..= 2S0 

of oxide of methyl 384 

of potassa 220 

of soda 230 

of silver 298 

Nitrates 124 

of mercury 302 

Nitre 220 

cubic 230 

sweet spirits of. 355 

Nitric acid 123 

acid, fuming 126 

ether 354 

oxide 126 

Nitrile-bases 455 

Nitro-benzamide 462 

Nitro-benzoic acid 397 

Nitro-benzol , 399, 462 

Nitro-chloronicene 463 

Nitro-coccusic acid 477 

Nitro-cumic acid 403 

Nitro-cumol 462 

Nitrogen 120 

binoxide of 126 

chloride of. 167 

compounds with oxygen 122 
estimation in organic 

bodies 324 

iodide of 167 

Nitro-naphthalase 462 

Nitro-phenasic acid 528 

Nitro-phenesic acid 528 

Nitro-phenisic acid 528 

Nitro-prussides 433 

Nitro-salicylamide 492 

Nitro-salicylic acid ... 406, 473 

Nitro-toluol 462, 495 

Nitro-toluylic acid 403 

Nitrous acid 126 

ether 355 

oxide 125 

Nitro-xylol 462 

Nomenclature 170 

Norium 352 

Notation, chemical 180 

Nutgalls 417 

Nutrition, plastic ele- 
ments of 520 

O. 

Octahedron 206 

(Euanthic acid 357 

ether 357 

(Enanthylic acid 395 

Oil gas 155 

of alliaria officinalis 493 

of aniseed 490 

of assafcetida 493 

of badian 491 

of bergamot 490 

of bitter almonds 396 

of bitter fennel 491 

of capivi 490 

of cedar wood 491 

of cinnamon 407 

of elemi 490 

of cubebs 490 

of cumin 491 

of garlic 493 

of gaultheria procum- 
bens 406, 491 



Oil — cont. Pagh 

of Guiana-laurel 490 

ofhops 490 

of horseradish 493 

of juniper 490 

of lavender 492 

oflemons , 490 

of meadow-sweet 404 

of mustard 492 

of onions 493 

of orange flowers 492 

of orange peel 490 

of pepper 490 

of peppermint 492 

of rosemary 492 

of rose petals 492 

of spirsea ulmaria 404 

ofturpentin 489 

of valerian 492 

of vitriol * 134 

of wine, heavy and light 362 

of wintergreen 491 

Oils 480 

drying or non-drying... 480 

volatile 488 

Olefiant gas 154 

and its compounds 362 

Oleic acid 482 

Olein 480,482 

Olive oil 488 

Onions, oil of 493 

Opiammon 445 

Opianic acid 445 

Opianine 446 

Opium 444 

Orange flowers, oil of 492 

oil of -peel 490 

Orcein 476 

Orcin 474, 476 

Organic bases 444 

bases, artificial 453 

substances, action of 

heat on 319 

substances, classifica- 
tion 319 

substances, composition 

elementary 316 

substances, decomposi- 
tion of. 319 

substances, ultimate 

analysis of. 320 

Orpiment 292 

Orsellinic acid 474,475 

Osmium .. 314 

Oxalate of oxide of methyl 384 

Oxalates 342 

Oxalic acid 341 

ether 356 

Oxalo-nitrile 461 

Oxalo-vinic acid 359 

Oxaluricacid 440 

Oxamethane 356 

Oxamethylane 384 

Oxamic acid 343 

ether 356 

Oxamide 343 

Oxanilic acid 461 

Oxanilide 461 

Oxide, cystic 443 

ofallyl 493 

of amyl, hydrated 388 

of benzoyl 396 

of bismuth 275 

of copper 2J7 



552 



INDEX 



Oxide — cont. Page 

of kakodyl 377 

of methyl 382 

of methyl, hydrated.... 381 
xanthic 443 

Oxides 109 

of antimony 288 

of chromium 267 

of gold 300 

of hydrogen 115 

of mercury 302 

of platinum 308 

of potassium 218 

of silver 297 

of sodium 224 

of zinc 273 

Oxygen 105 

-acids 201 

Oxy-hydrogen, flame and 

blowpipe 113 

safety-jet 161 

Oxy-salts 201 

Ozone 110 



Palladium, cyanide of 311, ■ 
Palmitate of oxide of me- 

lissyl - 

Palmitin 435 

Palmitic acid 485 

Palm-oil 484 

Papaverine 446 

Parabanic acid 440 

Paracyanogen 420 

Paraffin 523 

Parakakodylic oxide 380 

Paramagnetic bodies 89 

Paramide 345 

Paramorphine 446 

Paramylene 390 

Paranaphthalin 530 

Parapectin 340 

Paratartaric acid 413 

Parellic acid 476 

Parmelia parietina 476 

Pear, flavour of 389 

Pearlash 219 

Pectic acid 340 

Pectin 340 

Pel argonic acid 357, 395 

Pelopium 286 

Pentathionic acid 136 

Pepper, oil of 490 

Peppermint, oil of. 492 

Pepsin 521 

Perchlorate of potassa ... 222 

Perchloric acid 145 

Percussion-caps 429 

Periodic acid 148 

Peroxide of chlorine 144 

Persulphide of hydrogen. 165 

Peru balsam 408 

Peruvin 408 

Petalite 250 

Petinine 465 j 

Pettenkofer's bile-test 511 i 

Petroleum 531 

Petrolene 531 

Petuntze 255 

Phenetol 527 

i'henol 491, 526 

Phenyl 524 

alcohol 459, 527 

benzoaterf 527 



Phenyl — cont. Page 

chloride of. 527 

cyanide of 527 

hydrated oxide 526 

series, bases of. 459 

Phenyl-amine 459 

Philosophy, chemical 170 

Phloretin 406 

Phloridzin 406 

Phocenic acid 485 

Phorone 492 

Phosgene gas 131 

Phosphate of lime 241 

Phosphate of magnesia... 246 
of magnesia and ammo- 
nia 246 

Phosphate of soda 230 

Phospbethylic acid 359 

Phosphide of calcium 241 

Phosphobiethylic acid 359 

Phosphoretted hydrogen. 166 

Phosphoric acid 138 

acid, anhydrous 213 

acid, bibasic 213 

acid, glacial 213 

acid, monobasic 213 

acid, tribasic 212 

ether •... 354,359 

Phosphorous acid 138 

Phosphorus 137 

-bases 468 

chloride of 168 

compounds of 138 

Phosphovinic acid 358 

Photography 77 

Phthalic acid 529 

Picamar 524 

Picoline 465 

Picric acid 473, 52S 

Picro-erythrin 475 

Picrotoxin 452 

Pimaric acid 494 

Pinic acid 493 

Piperine 451 

Pitch 523 

mineral 531 

Pit-coal 530 

Plants, supply of carbon 

to 130 

Plaster of Paris 241 

Plate glass 252 

Platinum and its com- 
pounds 307 

analytical remarks 310 

bases 309 

black 307 

surface-action of.... 114, 115 

Plumbago 128 

Polarity, magnetic 86 

Polybasic acids 212 

Pontil or puntil 253 

Populin 452 

Porcelain 254 

clay 250 

Porphyroxine 446 

Potash 218 

crude 219 

Potassa 218 

acetate of 373 

alum 249 

analytical remarks on.. 224 

benzoate of ,. 397 

bicarbonate of. 220 

bisulphide of 221 1 



Potassa — cont. Page 

carbonate of. 219 

chlorate of. 221 

cyanate of. 426 

nitrate of. 220 

oxalate of .....; 342 

perchlorate of. 222 

sulphate of. 221 

tartrates of. 411 

urate of 438 

Potassium and its com- 
pounds 217 

bromide of. 224 

chloride of 223 

cyanide of 424 

ferricyanide of. 431 

ferrocyanide of. 433 

salicylide of. 404 

sulphides of 222 

sulphocyanide of. 434 

Potato-oil 488 

Precipitate, white 305 

Prehnite 250 

Proof-spirit 347 

Propione 376 

Propionic acid 376, 395 

Proportionals 174 

Proportions, multiple 173 

Propylene 388 

Protein 499 

binoxide of. 500 

teroxide of. 500 

Protide 500 

Protochloride of tin 2S3 

Protoxide of tin 382 

Prussian blue 432,433 

Prussiate of potash, red... 433 

yellow 431 

Prussic acid 420 

Pseudo-erythrin 475 

Pseudo-morphine 446 

Pudding 265 

Pii Una, water of. 541 

Purple of Cassius 283 

Purpurate of ammonia... 442 

Purpuric acid 442 

Purpurin 47S 

Purree 479 

Purreic acid 479 

Purrenone 479 

Pus 508 

Putrefaction 320 

Putty powder 282 

Pyrites 262 

Pyrmont, water of 540 

Pyroacetic spirit 376 

Pyro-acids 319 

Pyrobenzolin 466 

Pyrogallic acid 419 

Pyrogen acids 419 

Pyromeconic acid 447 

Pyromucic acid 345 

Pyrophorus of Homberg.. 249 

Pyrophosphoric acid 213 

Pyrotartaric acid 413 

Pyroxylic spirit 381 

Pyroxylin 344 

Q. 

Quercitron bark 479 

Quicksilver 301 

Quina 447 

Quinidine 448 

Quinine 447 



INDEX. 



553 



Page 

Quinine, amorphous 448 

Quincliue 464 

Quinoidine 448 

R. 

Radiation of heat 79 

Raceinic acid 413 

Realgar 292 

Red dyes 477 

Red fire 239 

Red lead 279 

Reflection of heat 79 

of light 71 

Refraction, double 75 

of light 72 

Rennet 499 

Resins 493 

Respiration 506 

elements of. 506 

Retinic acid 532 

Retinite 532 

Reverberatory furnace.... 158 

Rhodium 312 

Rhodizonic acid 345 

Ricinoleic acid 488 

Rocella tinctoria 474, 475 

Rocellinin 475 

Rochelle salt 411 

Rock oil 532 

Rock salt 232 

Roman alum 249 

Rosemary, oil of 492 

Rubia tinctorum 477 

Rubiacin 478 

Rubiacic acid 478 

Rubian 478 

Rubic acid 418 

Rust 260 

Ruthenium 314 

S. 

Saccharic acid 343 

Saccharic group 333 

Sacchulmic acid 336 

Sacchulmin 336 

Safety-lamp 161 

Safflower 478 

Saffron 479 

Sago 339 

Sal-alembroth 305 

Sal-ammoniac 233 

Salicin 403, 452 

Salicyl and its compounds 403 

hydride of 452 

Salicylate of oxide of me- 
thyl 491 

Salicylic acid 406 

Salicylides 404 

Salicylous acid 404 

Saligenin 405 

Saliretin 405 

Saliva 521 

Salsola soda 225 

Salt, definition 109 

of sorrel 342 

Salts, super or acid 202 

binary theory of 213 

constitution of 199 

double „ 202 

neutral 200 

Saltpetre 123, 220 

Sandarac 494 

Santonin 452 

47 



Pag 2 

Saponification 481 1 

Saratoga Congress spring 539 

Sarcosine 503 

Saturation 176 

Schlesischer Obersalz- 

brunnen 538 

Scheele ? s green 278 

Scagliola 241 

Sea-water 118 

Sebacic acid 484 

Seed lac 494 

Seggars 254 

Seidchutz, water of. 541 

Seignette salt 411 

Selenic acid 136 

Selenietted hydrogen 165 

Selenious acid 136 

Selenite 241 

Selenium 136 

Seleno-cyanogen 435 

Sellers, water of. 541 

Serpentine 247 

Serum of blood 504 

Silica 150 

Silicates of alumina 249 

of magnesia 247 

Silicic ether 355 

Silicium 149 

chloride of. 169 

fluoride of 150 

Silver, acetate of. 375 

analytical remarks 299 

benzoate of 397 

cyanide of 426 

fulminate of. 428 

its compounds 296 

standard of England.... 299 

Sikes ? hydrometer 535 

Sinapoline 467 

Sinnamine 467 

Size 502 

Shellac 494 

Skin 517 

Smee's battery 194 

Smalt 272 

Soap * 481 

Soap-stone 247 

Soap-test of Dr. Clark 241 

Soda, acetate of. 373 

alum 249 

analytical remarks on... 232 

ash 225 

ash, testing its value.... 228 

bicarbonate of. 226 

carbonate of. 225 

hydrate of. 224 

oxalate of 343 

tartrates of. 411 

urate of. 438 

Sodium 224 

cyanide of. 424 

ferro-cyanide of. 433 

oxides of. 224 

Solanine 450 

Solder 281 

Solids, expansion of 44 

Sorrel, salt of 342 

Spa Pouhon, water of 540 

Spar, calcareous 242 

Sparteine 450 

Specific gravities of metals 197 
gravity of solids and 
liquids 27 



Page 

Specific heat 66 

Speculum metal 279 

Spectrum 74 

Speiss 269 

Spermaceti 486 

Spirit from milk 509 

of Mindererus 373 

pyroxylic 381 

Spirits, table of spec. gr. 

of 537 

Spudomene 250 

Springs 118 

Starch 337 

State, change of, by heat.. 52 

Steambath 57 

Steam engine 57 

specific gravity of 118 

latent heat of 53 

Stearic acid. 7 481 

Stearin 481 

candles 482,483 

Stearoptene 489 

Steatite 247 

Steel 265 

Stibethyl 369, 469 

Sticklac 494 

Stillbite 250 

Stoneware 255 

Strontia 239 

acetate of. 373 

tartrate of 411 

Strontium and its com- 
pounds 239 

Strychnine 449 

Styphnic acid 479 

Styracin 408 

Styrol 408, 495 

Styrone 408 

Suberic acid 345,484 

Sublimate, corrosive 304 

Sublimation 58 

Substitution, law of. 317 

products, organic 317 

Succinic acid 484 

Sugar 333 

candy 334 

copper, test for the va- 
rieties of. 335 

from diabetes 335 

from diabetes insipidus 336 
from starch or dextrine 338 

gelatin- 402,501 

of lead „ 374 

of milk 336 

Sulphamylic acid 390 

Sulphasatyde 472 

Sulphate of alumina 249 

of ammonia 233 

of baryta 238 

of carbyl 365 

of copper 278 

oflime 241 

of magnesia 248 

of oxide of methyl 384 

ofpotassa 221 

of silver 298 

of soda 229 

of zinc 273 

Sulphates of mercury 303 

Sulphesatyde I. 472 

Sulphide of allyl 493 

of amyi.. 390 

of arsenic 292 



554 



INDEX 



Sulphide — cont. Page 

of barium 238 

of benzoyl .. 400 

of calcium 241 

of ethyl Sol 

of kakodyl 379 

of silver.... 299 

of sodium 231 

Sulphides 132 

of ammonium 234 

of antimony 289 

of mercury 306 

of potassium 222 

of tin 283 

test for 434 

Sulphindigotic acid 471 

Sulphindylic acid 471 

Sulphite of oxide of ethyl 354 

Sulphites 133 

Sulphobenzide 398 

Sulphobenzoic acid 397 

Sulphocyanide of allyl.... 493 

Sulphocyanides 434 

Sulphocyanogen and its 

compounds 434 

Sulphoglyceric acid 483 

Sulpholeic acid 487 

Sulphomethylic acid 383, 384 

Sulphomargaric acid 487 

Sulphonaphthalicacid 529 

Sulphophenic acid 526 

Sulphosaccharic acid 335 

Sulphotoluolic acid 495 

Sulphovinic acid 358 

decomposed by heat 359 

Sulphur 131 

acids 201 

auratum 2S9 

bases..... 201 

chloride of 168 

compounds with oxygen 132 
estimation in organic 

bodies 328 

salts 201 

Sulphuretted hydrogen... 163 

Sulphuric acid 133 

ether 354,366 

Sulphurous acid 132 

ether 354 

Super salts 202 

Surface -action of plati- 
num, charcoal, gold, 

&c... 114, 115, 128 

Sylvic acid 493 

Symbols 180 

Synthetical method of 

chemical research 115 

Systems of crystals 206 

Synaptase... 422 

T. 

Tannates 417 

Tannic acid 416, 417 

Tannin 416, 417 

Tanning 417, 517 

Tantalum 286 

Tapioca 339 

Tar 523 

mineral 531 

-oil stearin 523 

Tartar .. 410 

cream of 411 

emetic 2S8, 411 

•oluble.... 411 



Page 

Tartaric acid 410 

acid, anhydrous 412 

Tartralic acid .'. 412 

Tartrates 411 

Tartrelic acid 412 

Tartrovinic acid 359 

Taurin 511 

Tauro-cholalic acid 511 

Tauro-hyo-cholalic acid... 512 

Teeth 518 

Telluric acid 290 

Tellurium - 290 

Tellurous acid 290 

Tension 24 

Tension of vapours 59 

Terbium 251 

Terebene 490 

Terebylene 489 

Teroxide of protein 500 

Tetra-chloro-kinone 449 

Tetra-methyl-ammonium, 

hydrated oxide of 458 

Tetramyl-ammonium, hy- 
drated oxide of. 458 

Tetrathiomc acid 135 

Tetrethyl-ammonium, ox- 
ide of 456 

Thebaine.' 446 

Theine 450 

Theobromine 451 

Thermo-electrical pheno- 
mena 83 

Thermometer 42 

Thialdiue 370, 467 

Thionuric acid 441 

Thiosinnamine 466 

Thoria 252 

Thorite 252 

Thorium 252 

Tin 232 

analytical remarks on.. 283 

Tinned plate 284 

Tissue, membranous 516 

Titanium 287 

Tolene 495 

Tolu balsam 408,495 

Toluidine 462, 463 

Toluol 403,462,495 

Toluylic acid 403 

Tonka bean 406 

Trade winds 50 

Transmission of heat 82 

Travertin 242 

Triamylamine 458 

Triamyl-ammonia 458 

Tribasic acids 212 

Trichlor-aniline 460 

Trichloro-kinone 449 

Triethylamine 456 

Triethyl-ammonia 456 

Triethyl-stibin 469 

Trimethylamine 458 

Trimethyl-ammonia 45S 

Trithionic acid 135 

Trona 226 

Tungsten 284 

Turkey red 478 

Turmeric 479 

Turnbull's blue 433 

Turpentin 489 

common 489 

hydrated oil of. 490 

oil of. 489 



Turpentin — cont. Page 

Venetian 494 

Type metal 290 

Tyrosine 477, 497 

Twaddell's hydrometer.... 535 

U. 

Ulmicacid 336 

Ulmin 336 

Ultramarine... 231 

Upas antiar 452 

Uramile 441 

Uramilic acid 441 

Uranium 276 

Urates 438 

Urea 427,436 

Urethane 358 

Urethylane 384 

Uric acid 436,438,515 

products from 436 

Urinary calculi 443, 515 

Urine 512 

Urinometer 32 

Usnea barbata 476 

Usnic acid 476 

V. 

Valeracetonitrile 501 

Valeramide 391 

Valerianic acid 390,492 

ether 357 

Valerian, oil of 492 

Valeric acid 390, 395, 492 

Valerene 483 

Valerol 492 

Valeronitrile 391, 501 

Valyl 392 

Vanadium 285 

Vapour of water, tension. 536 
Vapours, determination of 

the density of. 330 

maximum density of.... 60 

tension of. 59 

Varec 225 

Variolaria 474 

Varvicite 258 

Vegetable acids 410 

nutrition 522 

Vegetc-alkalis 444 

Venous blood 503 

Ventilation 51 

Veratria 449 

Veratrine 449 

Verdigris 374 

Verditer 278 

Vermilion 306 

Vinous fermentation 346 

Viscous fermentation 351 

Vitriol, blue 278 

green 262 

oil of 134 

oil of, fuming 134 

Volatile oils 488 

Volume, combination by. 177 

equivalent 17S 

Voltaic battery 98 

pile, chemistry of the... 1S7 

Voltameter 190 

Volta's pile ~ 98 

W. 

Wash, distiller's 348 

Water 115 

analysis of ..... 115 



INDEX. 



555 



Water — conl. Page 

distilled 118 

expansion by heat 47 

hardness of 241, 212 

of crystallization 202 

oxygenated 119 

tension of its vapour.... 59 

Wax 486 

fossil 532 

Weights 542 

specific 27 

Welding 199 

Whey 499, 508 

White lead 280 

precipitate 305 

vitriol 273 

Winds 50 

Wine 347 

clarifying of. 502 

Wintergreen oil 406 

Witherite 238 



Page 

Wolframium 284 

Wood ether 382 

spirit 3S1 

Woody tissue 341 

Wootz 2P8 

Wort 348 

X. 

Xanthic acid 368 

oxide 443, 516 

Xanthin 478 

Xanthorrhoeahastilis 473 

Xylidine 462 

Xylite 388 

Xyloidin 341 

Xylol 348 

Y. 
Yeast 346, 348 



Page 

Yellow dyes 477 

Yttria 251 

Yttrium 251 

Z. 

Zaffer 272 

Zeise's combustible pla- 
tinum salt 365 

Zeolites 250 

Zinc 272 

analytical remarks 273 

cyanide of. 426 

-ethyl 368 

fulminate of. 429 

lactate of. 351 

Zinin's process 479 

Zircon 252 

Zirconia ....'. 252 

Zirconium 252 



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DUNGLISON, FORBES, TWEEDIE, AND CONOLLY.— The Cyclopaedia of Practical Medi- 
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Therapeutics, Diseases of Women and Children, Medical Jurisprudence, &c &c. In four 
large super-royal octavo volumes, of 3254 double-columned pages, strongly and hand- 
somely bound. 

* # * This work contains no less than four hundred and eighteen distinct treatises, contri- 
buted by sixty-eight distinguished physicians. 



DUNGLISON (ROBLEY), M. D. — MEDICAL Lexicon; a Dictionary of Medical Science, con- 
taining a concise Explanation of the various Subjects and Terms of Physiology, Pathology, 
Hygiene, Therapeutics, Pharmacology, obstetrics. Medical Jurisprudence, &c. With the 
French and other Synonymes; Notices of Climate and of celebrated Mineral Waters; For- 
mulae for various Officinal. Empirical, and Dietetic Preparations, &c. Thirteenth edition, 
revised. In one very thick octavo volume, of over 900 large double-columned pages, 
etrongly bound in leather, with raised bands. (Just Issued.) 



BLANCH ARD & LEA'S MEDICAL PUBLICATIONS. 5 

DUNGLTSON (ROBLEY). M.D.— Tee Practice of Medicine. A Treatise on Special Pathology 
and Therapeutics. Third edition. In two large octavo volumes, of 1500 pages. 



DUNGLTSON (ROBLEY), TNT. D.— General Therapeutics and Materia Medica: adapted for a 
Medical Text-book. Fifth edition, much improved. With one hundred and eighty-seven 
illustrations. In two large and handsomely printed octavo volumes, of about 1100 pages. 
(Just Issued.) 



TDUNGLISON (ROBLEY), M. D. — New Remedies, with Formula for their Preparation and 
Administration. Seventh Edition, with extensive Additions. In one very large octavo 
volume, of 770 pages. (Now Beady.) 



DUNGLTSON (ROBLEY), M.D.— Human Physiology. Eighth edition. Thoroughly revised 
and extensively modified and enlarged, with over 600 illustrations. In two large and 
handsomely printed octavo volumes, containing about 1500 pages. 



DICKSON (S. II.), M. D.— Elements op Medicine: a Compendious View of Pathology and 
Therapeutics, or the History and Treatment of Diseases. In one large and handsome 
octavo volume of 750 pages, leather. (Just Issued.) 



DE JONGH (L. J.), M.D.— The Three Kinds of Cod-Liver Oil. comparatively considered, with 
their Chemical and Therapeutic, Properties. Translated, with an Appendix and Cases, by 
Edward Carey, M. D. To which is added an article on the subject from " Dunglison on 
New Remedies." In one small 12mo. volume, extra cloth. 



DAY (GEORGE E.), M. D.— A Practical Treatise on the Domestic Management and morb 
Important Diseases of Advanced Life. With an Appendix on a new and successful modo 
of treating Lumbago and other forms of Chronic Rheumatism. One volume octavo, 228 
pages. 

ELLIS (BENJAMIN), M. D.— The Medical Formulary; being a Collection of Prescriptions, 
derived from the writings and practice of many of the most eminent physicians of America 
and Europe. Together with the usual Dietetic Preparations and Antidotes for Poisons. 
To which is added an Appendix on the Endermicuse of Medicines, and on the use of Ether 
and Chloroform. The whole accompanied with a few brief Pharmaceutic and Medical 
Observations. Tenth edition, revised and much extended, by Robert P. Thomas, M.D., 
Professor of Materia Medica in the Philadelphia College of Pharmacy. In one neat octavo 
■volume of 296 pages. 



ERICHSEN (JOHN).— The Science and Art of Surgery; being a Treatise on Surgical Inju- 
ries, Diseases, and Operations. With Notes and Additions by the American editor. Illus- 
trated with over 300 engravings on wood. In one large and handsomo octavo volume of, 
nearly 900 closely printed pages. 



FLTNT (AUSTIN), M. D— Physical Exploration and Diagnosis a? Diseases affecting thh 
Respiratory Organs. In one handsome octavo volume, extra cloth, of 636 pages. (Now 
Ready.) 



FERGUSSON (WILLIAM), F.R. S.— A System of Practical Surgery. Fourth American, from 
the third and enlarged London edition. In one large and beautifully printed octavo 
volume of about 700 pages, with 393 handsome illustrations. 



FRICK (CHARLES), M.D.— Renal Affections : their Diagnosis and Patkology. With illus- 
trations. One volume, royal 12mo., extra cloth. 



FOWNES (GEORGE), PH. D. — Elementary Chemistry, Theoretical and Practical. With, 
numerous illustrations. A new American, from the last and revised London edition. 
Edited, with Additions, by Robert Bridges, M.D. In one large royal 12mo. volume, of 
over 550 pages, with 181 wood-cute : sheep, or extra cloth. (Now Ready.) 



6 BLANCHARD & LEA'S MEDICAL PUBLICATIONS. 

GRAHAM (THOMAS), F. It. S.— The Elements of Chemistry. Including the Application of 
the Science to the Arts. With numerous illustrations. With Notes and Additions, by 
Robert Bridges, M. D., etc., etc. Second American, from the second and enlarged London 
edition. 

PART I. (Lately Issued) large 8vo., 430 pages, 185 illustrations. 

PART II. (Preparing) to match. 



CROSS (SAMUEL D.), M.D.— A Practical Treatise on the Diseases, Injuries, and Malfor 

MATIONS OF THE URINARY BLADDER, THE PROSTATE GLAND, AND THE URETHRA. Second edition 

revised and much enlarged, with 184 illustrations. In one very large and handsome octav* 
volume of over 900 pages, extra cloth or leather. (Just Issued.) 



GROSS (SAMUEL P.), M.P.— A Practical Treatise on Foreign Bodies in the Air-Passage? 
In one handsome octavo volume, with illustrations. 



GROSS (SAMUEL P.), M.P. — Elements of Pathological Anatomy; illustrated by colore* 
engravings and 250 wood-cuts. Second and revised edition. In one large imperial octav# 
volume of 822 pages, leather. 



GROSS (SAMUEL P.), M.D.— A System of Surgery; Piagnostic, Pathological, Therapeutic, 
and Operative. With very numerous engravings on wood. (Preparing.) 



GLUGE (GOTTLIEB), M.D.— An Atlas of Pathological Histology. Translated, with Notes 
and Additions, by Joseph Leidy, M. D., Professor of Anatomy in the University of Penn- 
sylvania. In one volume, very large imperial quarto, with 320 figures, plain and colored, 
on twelve copper-plates. 



GRIFFITH (ROBERT E.), M.P.— A Universal Formulary, containing the Methods of Pre- 
paring and Administering Officinal and other Medicines. The whole adapted to Physicians 
and Pharmaceutists. Second edition, thoroughly revised, with numerous Additions, by 
Robert P. Thomas, M. P., Professor of Materia Medica in the Philadelphia College of Phar- 
macy. In one large and handsome octavo volume of over 600 pages, double columns. 



GRIFFITH (ROEERT E.), M. D.— Medical Botany ; or, a Pescription of all the more impor- 
tant Plants used in Medicine, and of their Properties, Uses, and Modes of Administration. 
In one large octavo volume of 704 pages, handsomely printed, with nearly 350 illustrations 
on wood. 



GARDNER (P. PEREIRA), M. D— Medical Chemtstfy, for the use of Students and the Pro- 
fession: being a Manual of the Science, with its Applications to Toxicology, Physiology, 
Therapeutics, Hygiene, &c. In one handsome royal 12mo. volume, with illustrations. 



HASSE (C. E.), M. D— An Anatomical Description of the Diseases of Respiration and Cir- 
culation. Translated and edited by Swaine. In one volume, octavo. 



HARRISON (JOHN), M.D.— An Essay towards a Correct Theory of the Nervous System 
In one octavo volume, 292 pages. 

HUGHES (H. M.), M.D. — A Clinical Introduction to the Practice of Auscultation, and 
other Modes of Physical Diagnosis, in Diseases of the Lungs and Heart. Second American 
from the second and improved London edition. In one royal 12mo. volume. (Just Heady.) 



nORNER (WILLIAM E.), M. D.— Special Anatomy and Histology. Eighth edition. Exten- 
sively revised and modified. In two large octavo volumes, of more than 1000 pages, hand- 
somely printed, with over 300 illustrations. 



HOBLYN (RICHARD D.\ A. M.— A Dictionary of the T^.rms used tn Medicine and the Col. 
lateral Sciences. Second and improved American edition. Revised, with numerous Ad- 
ditions, from the second London edition, by Isaae Hays, M. D., &c. In one large royal 
12mo. volume, of over 600 pages, double columns. {Now Heady.) 



BLANCHARD & LEA'S MEDICAL PUBLICATIONS. 7 

HAMILTON (FRANK II.) — A Treatise on Fractures and Dislocations. In one handsome 
octavo volume. With numerous illustrations. {Preparing.) 



HERSCHEL (SIR JO TIN F. W.), F. R. S.— Outlines of Astronomy. New American, from the 
third London edition. In one neat volume, crown octavo, with six plates and numerous 
wood-cuts. 



HUMBOLDT (ALEXANDER). — Aspects of Nature tn Different Lands and Different Cli- 
mates. Second American edition, one vol. royal 12mo., extra cloth. 



JONES (T. WHARTON), F.R. S— The Principles and Practice of Ophthalmic Medicine and 
Surgery. Second American, from the second and revised English edition. With Addition« 
by Edward Ilartshorne, M.D. In one very neat volume, largo royal 12mo., of 500 pages, 
with 110 illustrations. 



JONES (C. nANDFIELD), F.R. S., AND EDWARD H. SIEYEKING, M.D.— A Manual of 
Pathological Anatomy. With 397 engravings on wood. In one handsome volume, octavo, 
of nearly 750 pages, leather. {Lately Issued.) 



KIRKES (WILLIAM SENHOCSE), M.D., AND JAMES PAGET, F.R.S.— A Manual of Phy- 
siology. Second American, from the second and improved London edition. With 165 
illustrations, in one large and handsome royal 12mo. volume. 550 pages. 



KNAPP (F.), PH. D.— Technology ; or, Chemistry applied to the Arts and to Manufactures. 
Edited, with numerous Notes and Additions, by Dr. Edmund Ronalds and Dr. Thomas 
Richardson. First American edition, with Notes and Additions, by Professor Walter R. 
Johnson. In two handsome octavo volumes, printed and illustrated in the highest style 
of art. with about 500 wood-engravings. 



LETIMANN (G. C.) — Physiological Chemistry. Translated from the second edition by George 
E. Day, M.D. Edited by R. E. Rogers, M.D. With illustrations selected from Funke's 
Atlas of Physiological Chemistry, and an Appendix of Plates. Complete in two handsome 
octavo volumes, extra cloth, containing 1200 pages. With nearly 200 illustrations. {Just 
Issued.) 



LEHMANN (G. C.) — Manual of Chemical Physiology. Translated from the German, with 
Notes and Additions, by J. C. Morris, M. D. With an introductory Essay on Vital Force, 
by Samuel Jackson, M.D. In one handsome octavo volume, extra cloth, of 336 pages. 
With numerous illustrations. {Now Ready.) 



LEE (ROBERT), M. D.— Clinical Midwifery; comprising the Histories of Five Hundred and 
Forty-five Cases of Difficult, Preternatural, and Complicated Labor, with Commentaries. 
From the second London edition. In one royal 12mo. volume, extra cloth, of 238 pages. 



LA ROCHE (R.), M.D.— Pneumonia; its Supposed Connection, Pathological and Etiological, 
with Autumnal Fevers, including an Inquiry into the Existence and Morbid Agency of 
Malaria. In one handsome octavo volume, extra cloth, of 500 pages. 



LA ROCHE (R.), M.D.— Yellow Fever, considered in its Historical, Pathological, Etiological, 
and Therapeutical Relations. Including a Sketch of the Disease as it has occurred in 
Philadelphia from 1699 to 1854. with an Examination of the Connections between it and 
the Fevers known under the same name in other Parts of Temperate, as well as in Tropical 
Regions. In two large and handsome octavo volumes, of nearly 1500 pages, extra cloth. 
{Just Issued.) 



LAWRENCE (W.), F.R. S.— A Treatise on Diseases of the Eye. A new edition, edited, with 
numerous Additions, and 243 illustrations, by Isaac Hays, M. D.. Surgeon to Wills' Hos- 
pital, etc. In one very large and handsome octavo volume of 950 pages, strongly bound 
in leather, with raised bands. 



8 BLANCHAED & LEA'S MEDICAL PUBLICATIONS. 

LALLEMAND (M.).— The Causes, Symptoms, and Treatment of Spermatorrhoea. Translated 
and edited Ly Henry J. McDougal. In one volume, octavo, of 320 pages. Second Ame- 
rican edition. 



LARDNER (DIONYSIUS), D.C.L. — Handbooks op Natural Philosophy and Astronomy. 
Revised, with numerous Additions, by the American editor. First Course, containing 
Mechanics, Hydrostatics, Hydraulics, Pneumatics, Sound, and Optics. In one large royal 
12mo. volume, of 750 pages, with 42-4 wood-cuts. Second Course, containing Heat, Elec- 
tricity. Magnetism, and Galvanism, one volume, large royal 12mo., of 450 pages, with 250 
illustrations. Third Course (now ready), containing Meteorology and Astronomy, in one 
large volume, royal 12mo., of nearly 800 pages, with 37 plates and 200 wood-cuts. The 
whole complete in three volumes, of about 2000 large pages, with over 1000 figures on steel 
and wood. 



METGS (CHARLES D.), M. D.— Woman: her Diseases and their Remedies. A Series of Lec- 
tures to his Class. Third and improved edition. In one large and beautifully-printed 
octavo volume. 



MEIGS (CHARLES D.), M. D. — Obstetrics : the Science and the Art. Second edition, 
revised and improved. With 131 illustrations. In one beautifully-printed octavo volume, 
of 752 large pages. 



MEIGS (CHARLES D.), M. D. — A Treatise on Acute and Chronic Diseases op the Neck op 
the Uterus. With numerous plates, drawn and colored from nature, in the highest stylo 
of art. In one handsome octavo volume, extra cloth. 



MEIGS (CHARLES D.), M. D.— Observations on Certain of the Diseases of Young Children. 
In one handsome octavo volume, of 214 pages. 



MEIGS (CHARLES D.), M.D.— On the Nature. Signs, and Treatment of Childbed Eever; 
in a Series of Letters addressed to the Students of his Class. In one handsome octavo 
volume, extra cloth, of 365 pages. 



MILLER (JAMES). E. R. S. E.— Principles of Surgery. Fourth American, from the third and 
revised Edinburgh edition. In one large and very beautiful volume of 700 pages, with 240 
exquisite illustrations on wood. 



MILLER (JAMES), F.R.S.E.— The Practice of Surgery. Third American, from the second 
Edinburgh edition. Edited, with Additions, by F. W. Sargent. M. D., one of the Surgeons 
to Wills' Hospital, etc. Illustrated by 319 engravings on wood. In one large octavo 
volume of over 700 pages. 



MALGATGNE (J. F.). — Operative Surgery, based on Normal and Pathological Anafomy. 
Translated from the French, by Frederick Brittan, A. B., M. D. With numerous illustra- 
tions on wood. In one handsome octavo volume, of nearly 600 pages. 



MOITR (FRANCIS), Pn. D., AND REDWOOD (TTTEOPHILUS).— Practical Pharmacy. Com- 
prising the Arrangements, Apparatus, and Manipulations of the Pharmaceutical Shop 
and Laboratory. Edited, with extensive Additions, by Prof. William Procter, of the Phi- 
ladelphia College of Pharmacy. In one handsomely-printed octavo volume, of 570 pages, 
with over 500 engravings on wood. 

MACLISE (JOSEPH).— Surgical Anatomy. Forming one volume, very large imperial quarto. 
With sixtv-eight large and splendid Plates, drawn in the best style, and beautifully 
colored. Containing 190 Figures, many of them the size of life. Together with copious 
and explanatory letter-press. Strongly and handsomely bound in extra cloth, being one 
of the cheapest and best executed Surgical works as yet issued in this country. 
Copies can be sent by mail, in fivo parts, done up in stout covers. 



BLANCHARD & LEA'S MEDICAL PUBLICATIONS. 9 

MAYNE (JOHN), M.D. — A Dispensatory and Therapeutical Remembrancer. Comprising 
the entire lists of Materia Medica, with every Practical Formula contained in the threa 
British Pharmacopoeias. In one 12mo. volume, extra cloth, of over 300 large pages. 



MACKENZIE (W.), M. D. — A Practical Treatise on Diseases and Injuries of the Eye. To 
which is prefixed an Anatomical Introduction, hy T. Wharton Jones. From the fourth 
revised and enlarged London edition. With Notes and Additions by Addinell Hewson, 
M.D. In one very large and handsome octavo volume, with numerous wood-cuts and 
plates. 1028 pages, leather, raised bands. (Just Issued.) 

NEILL (JOHN), M. D., AND FRANCIS GURNET SMITH, M. D.— An Analytical Compendium 
of the various Branches of Medical Science; for the Use and Examination of Students. 

I Second edition, revised and improved. In one very large and handsomely printed royal 
12mo. volume of over 1000 pages, with 350 illustrations on wood. Strongly bound in 
leather, with raised bands. 



NEILL (JOHN), M. D.— Outlines of the Arteries. 1 vol. 8vo., handsome colored plates. 

Outlines of the Nerves. 1 vol. 8vo., with handsome plates. Outlines of the Veins and 

Lymphatics, 1 vol. 8vo., handsome colored plates. 
Also, the three works done up in one handsome volume, half bound. 

NELIGAN (J. MOORE), M.D. — Atlas of Cutaneous Diseases. In one beautiful quarto 
volume, extra cloth, with splendid colored plates, presenting nearly one hundred elaborate 
representations of disease. (Noiu Ready.) 

NELIGAN (J. MOORE), M. D.— A Practical Treatise on Diseases op the Skin. In one neat 
royal 12mo. volume, of 334 pages. 

OWEN (PROF. R.)— On the Different Forms of the Skeleton. One royal 12mo. volume, 
with numerous illustrations. 



PANCOAST (J.), M.D. — Operative Surgery; or, A Description and Demonstration of the 
various Processes of the Art; including all the New Operations, and exhibiting the state 
of Surgical Science in its present advanced condition. Complete in one royal 4to. volume 
of 380 pages of letterpress description and eighty large 4to. plates, comprising 486 illus- 
trations. Second edition, improved. 



PARKER (LANGSTON).— The Modern Treatment of Syphilitic Diseases, both Primary and 
Secondary: comprising the Treatment of Constitutional and Confirmed Syphilis, by a safe 
and successful method. With numerous Cases, Formulas, and Clinical Observations. 
From the third and entirely rewritten London edition. In one neat octavo volume. 



PEREIRA (JONATHAN), M. D.— The Elements of Materia Medica and Therapeutics. Third 
American edition, enlarged and improved by the author; including Notices of most of the 
Medical Substances in use in the civilized world, and forming an Encyclopaedia of Materia 
Medica. Edited, with Additions, by Joseph Carson, M. D., Professor of Materia Medica and 
Pharmacy in the University of Pennsylvania. In two very large octavo volumes of 2100 
pages, on small type, with over 450 illustrations. (Now Complete.) 



PARRISH (EDWARD).— An Introduction to Practical Pharmacy. Designed as a Text-book 
for the Student, and as a Guide for the Physician and Pharmaceutist. With many For- 
mulae and Prescriptions. In one handsome octavo volume, extra cloth, of 550 pages, 
with 243 illustrations. (Now Ready.) 



PEASELEE (E. R.). M. D.— Human Histology, in its Applications to Physiology and General 
Pathology, designed as a Text-book for Medical Students. With numerous illustrations. 
In one handsome royal 12mo. volume. (Preparing.) 



PIRRIE (WILLIAM), F. R. S. E.— The Principles and Practice of Surgery. Edited by John 
Neill, M.D., Demonstrator of Anatomy in the University of Pennsylvania, Surgeon to the 
Penusj'lvania Hospital, etc. In one very handsome octavo volume of 780 pages, with 316 

lions. 



illustratf 



R A MSBOTH AM (FRANCIS H.), M.D.— The Principles and Practice of Obstetric Medicine 
and Surgery, in reference to the Process of Parturition. A new and enlarged edition, 
thoroughly revised by the author. With Additions by W. V. Keating, M.D. In one lai'ge 
and handsome imperial octavo volume of 650 pages, strongly bound in leather, with raised 
bands. With sixt3 r -four beautiful plates, and numerous wood-cuts in the text, containing 
in all nearly 200 large and beautiful figures. (Just Issued.) 



10 BLANCHARD & LEA'S MEDICAL PUBLICATIONS. 

RICORD (P.), M.D.— Illustrations op Syphilitic Disease. Translated from the French, hy 
Thomas F. Betton, M.D. With the addition of a History of Syphilis, and a complete Bihli 
ogrtfphy aud Formulary of Remedies, collated and arranged by Paul B. Goddard, M.D. 
With fifty large quarto plates, comprising 117 beautifully colored illustrations. In one 

• large and handsome quarto volume. 



RICORD (P.), M.D.— A Treatise on the Tenereal Disease. By John Hunter, F.R.S. With 
copious Additions, by Ph. Ricord, M.D. Edited, with Notes, by Freeman J. Bumstead, 
M.D. In one handsome octavo 'volume, with plates. 



RICORD (P.), M.D.— Letters on Syphilis, addressed to the Chief Editor of the Union Medi- 
cale. With an Introduction, by Amedee Latour. Translated by W. P. Lattimore, M.D. 
In one neat octavo volume. 



ROKITANSKY (CARL). — A Manual op Pathological Anatomy. Translated from the Ger- 
man by W. E. Swaine, Edward Sieveking, M.D., C. H.Moore, and George E. Day, M.D. 
Complete, four volumes bound in two, extra cloth, of about 1200 pages. (Just Issued.) 



RIGBY (EDWARD), M. D.— A System of Midwifery. With Notes and Additional Illustra- 
tions. Second American edition. One volume octavo, 422 pages. 



ROYLE (J. FORBES), M.D. — Materia Medica and Therapeutics; including the Preparations 
of the Pharmacopoeias of London, Edinburgh, Dublin, and of the United States. With 
many new Medicines. Edited by Joseph Carson, M.D., Professor of Materia Medica and 
Pharmacy in the University of Pennsylvania. With ninety-eight illustrations. In one 
large octavo volume of about 700 pages. 



SKEY (FREDERICK C), F. R. S.— Operative Surgery. In one very handsome octavo volume 
of oyer 650 pages, with about 100 wood-cuts. 



SHARPEY (WILLIAM), M.D., JONES QUAIN, M.D., AND RICHARD QUAIN, F.R. S., etc.— 
Human Anatomy. Revised, with Notes and Additions, by Joseph Leidy, M.D. Complete 
in two large octavo volumes, of about 1300 pages. Beautifully illustrated with over 500 
engravings on wood. 



SMITH (HENRY H.), M. D., AND WILLIAM E. HORNER, M. D.— An Anatomical Atlas 
illustrative of the Structure of the Human Body. In one volume, large imperial octavo, 
with about 650 beautiful figures. 



SMITH (HENRY H.), M.D.— Minor Surgery; or, Hints on the Every-day Duties of the 
Surgeon. With 247 illustrations. Third and enlarged edition. In one handsome royal 
12mo. volume of 456 pages 



SARGENT (F. W.), M.D.— On Bandaging and other Operations op Minor Surgery. Second 
edition, enlarged. In one handsome royal 12mo. volume of nearly 400 pages, with 182 
illustrations. (Just Issued.) 

STILL15 ('ALFRED), M. D.— Principles op Therapeutics. In one handsome volume. (Pre- 
paring)) 



SIMON (JOHN), F.R.S.— General Pathology, as conducive to the Establishment of Rational 
Principles for the Prevention and Cure of Disease. A Course of Lectures delivered at St. 
Thomas's Hospital during the Summer Session of 1850. In one neat octavo volume. 



SMITH (W. TYLER), M. D.— On Parturition, and the Principles and Practice of Obstetrics. 
In one large duodecimo volume of 400 pages. 



SMITH (W. TYLER), M.D.— The Pathology and Treatment of Leucorrhcea. With nume- 
rous illustrations. In one very handsome octavo volume, extra cloth, of about 250 pages. 



BLANCHARD & LEA'S MEDICAL PUBLICATIONS. 11 

SOLLY (SAMUEL), F. F.S. — TnE Human Brain; its Structure, Physiology, and Diseases. 
With a Description of the Typical Forms of the Brain iu the Animal Kingdom. From the 
Second and much enlarged London edition. In one octavo volume, with 12(J wood-cuts. 



SCIKEDLER (FRIEDRICH), Ph. D.— The Boos of Nature; an Elementary Introduction to 
the Sciences of Physics, Astronomy, Chemistry, Mineralogy, Geology. Botany. Zoology, and 
Physiology. First American edition, with a Glossary and other Additions and Improve- 
ments; from the second EnglislT~edition. Translated fron* the sixth German edition, by 
Henry Medlock, F.C.S., <fcc. In one thick volume, small octavo, of about 700 pages, with 
679 illustrations on wood. Suitable for the higher schools and private students. (JVoio 
Heady) 

TAYLOR (ALFRED S.), M.D., F.R. S.— Medical Jurisprudence. Fourth American, from the 
fifth and improved English edition. With Notes and References to American Decisions, 
by Edward Hartshorne, M. D. In one large octavo volume of 700 pages. (JFoiv Heady.) 



TAYLOR (ALFRED S.), M. D. — On Poisons, in Relation to Medical Jurisprudence and Medi- 
cine. Edited, with Notes and Additions, by R. E. Griffith, M.D. In one large octavo 
volume of 6S8 pages. 



TANNER (T. H.). M. D. — A Manual of Clinical Medicine and Physical Diagnosis. To which 
is added, The Code of Ethics of the American Medical Association. In one neat volume, 
fcmall 12mo., extra cloth, or flexible. (Just Issued.) 



TOMES (JOHN), F.R.S.— A Manual of Dental Practice. Illustrated by numerous engravings 
on wood. In one handsome volume. (Preparing.) 



TODD (R. B.), M.D., AND WILLIAM BOWMAN, F.R. S. — Physiological Anatomy and Physi- 
ology of Man. "With numerous handsome wood-cuts. Parts I., II., and III., in one octavo 
volume, 552 pages. Part IV. will complete the work. 



WATSON (THOMAS), M.D., &c — Lectures on the Principles and Practice of Physic. 
Third American, from the last Loudon edition. Revised, with Additions, by D. Francis 
Condie, M.D., author of a "Treatise on the Diseases of Children," &c. In one octavo 
volume, of nearly 1100 large pages, strongly bound, with raised bands. 



WALSHE (W. II.), M.D. — Diseases or the Heart, Lungs, and Appendages; their Symptoms 
and Treatment. In one handsome volume, large royal 12mo., 512 pages. 



What to Observe at the Bedside and after Death, ln Medical Cases. Published under the 
authority of the London Society for Medical Observation. In one very handsome volume, 
royal 12mo., extra cloth. 



WTLDE (W. R.).— Aural Surgery, and the Nature and Treatment of Diseases of the Ear. 
In one handsome octavo volume, with illustrations. 



WHITEHEAD (JAMES), F.R. C. S., Ac — The Causes and Treatment of Abortion and Ste- 
rility: beinc: the Result of an Extended Practical Inquiry into the Physiological and 
Morbid Conditions of the Uterus. Second American Edition. In one volume, octavo, 308 
pages 



WEST (CnARLES), M.D. — Lectures on tub Diseases of Infancy and Childhood. Second 
American, from the second and enlarged London edition. In one volume, octavo, of nearly 
500 pages. 



12 BLANCIIARD & LEA'S MEDICAL PUBLICATIONS. 

WEST (CHARLES), M.D.— An Inquiry into the Pathological Importance of Ulceration op 
the Os Uteri. Being the Croonian Lectures for the year 1854. In one neat octavo volume, 
extra cloth. 



WEST (CHARLES), M. D.— Lectures on the Diseases of Women. In two Parts. Part I, 
Diseases of the Uterus: Part II, Diseases of ihe Ovaries, etc., the Bladder, Vagina, and 
External Organs. 

%* Publishing in the "Medical News and Library" for 1856 and 1857. 



WILSON (ERASMUS), M.D.. E. R.S.— A System of Human Anatomy, General and Special. 
Fourth American, from the last English edition. Edited by Paul B. Goddard, A.M., M.D. 
With 250 illustrations. Beautifully printed, in one large octavo volume, of nearly 600 
pages. 



WILSON (ERASMUS), M.D., F.R.S.— The Dissector's Manual; Practical and Surgical Ana- 
tomy. Third American, from the last revised and enlarged English edition. Modified and 
rearranged by William Hunt, M.D. In one large and handsome royal 12mo. yolunie, 
leather, of 582 pages, with 154 illustrations. (Now Heady.) 



WILSON (ERASMUS), M.D., F. R. S.— On Diseases of the Skin. Third American, from the 
third London edition. In one neat octavo volume, of about 500 pages, extra cloth. 



WILSON (ERASMUS), M.D., P. R.S. — On Constitutional and Hereditary Syphilis, and on 
Syphilitic Eruptions. In one small octavo volume, beautifully printed, with four exqui- 
site colored plates, presenting more than thirty varieties of Syphilitic Eruptions. 

WILSON (ERASMUS), M. D., F.R. S.— Healthy Skin; a Treatise on the Management of the 
Skin and Hair in Relation to Health. Second American, from the fourth and improved 
London edition. In one handsome royal 12mo. volume, extra cloth, with numerous illus- 
trations. Copies may also be had in paper covers, for mailing, price 75 cents. (Now Ready) 



WILLIAMS (C. J. B.), M.D., F.R.S.— Principles of Medicine; comprising General Pathology 
and Therapeutics, and a brief general view of Etiology, Nosology, Semeiology. Diagnosis, 
Prognosis, and Hygienics. Edited, with Additions, by Meredith Clymer. M.D. Fourth 
American, from the last and enlarged London edition. In one octavo volume, of 476 pages. 



WILLIAMS (C. J. B.), M. D., F.R.S.— A Practical Treatise on Diseases of the Respiratory 
ORGANS; including Diseases of the Larynx. Trachea, Lungs, and Pleurae. With numerous 
Additions and Notes, by M. Clymer, M.D. With wood-cuts. In one octavo volume, pp. 508. 

YOU ATT (WILLIAM), V.S. — The Horse. A new edition, with numerous illustrations; 
together with a General History of the Horse; a Dissertation on the American Trotting 
Horse; how Trained and Jockeyed; an Account of his Remarkable Performances; and an 
Essay on the Ass and the Mule. By J. S. Skinner, formerly Assistant Postmaster-General, 
and Editor of the Turf Register. One large octavo volume. 



YOUATT (WILLIAM), V. S.— The Dog. Edited by E. J. Lewis, M. D. With numerous and 
beautiful illustrations. In one very handsome volume, crown Svo., crimson cloth, gilt 



Blanehard & Lea have now readv a del ailed Catalogue of their publications, in Medical and 
other Sciences, with Specimens of the Woodstengravifigs, Notices of the Press, &e. &c, forming 
n pamphlet of sixty-four larire octavo pages. 1 1 has been prepared without regard to expense, 
and may be considered as one of the handsomest specimens ot printing as yet executed m 
thi* country. Copies will be sent free, by post, on receipt of two three-cent postage stamps. 

Detailed Catalogues of their publications, Miscellaneous, Educational, Medical, &c, fur- 
nished gratis, on application. 



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